JP2013089456A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system that allows rapid activation and effective operation control.SOLUTION: A fuel cell system comprises: a solid oxide fuel cell 2 that has a fuel electrode 21 to which fuel gas is supplied and an air electrode 22 to which air is supplied; a generator 6 that is provided separately from the solid oxide fuel cell 2; a reformer 1 that reforms fuel gas containing a hydrocarbon compound and supplies the reformed fuel gas to the fuel electrode 21 of the solid oxide fuel cell 2; an internal combustion engine 3 that drives the generator 6 and heats the solid oxide fuel cell 2 with exhaust gas thereof; and control means that controls fuel supply to the internal combustion engine 3. The internal combustion engine 3 has: a first port 31 that allows the fuel and the air to enter the internal combustion engine 3 from outside without passing through the solid oxide fuel cell 2; and a second port 32 that is provided separately from the first port 31 and allows exhaust gas of the fuel electrode 21 of the solid oxide fuel cell 2 to enter the internal combustion engine 3.

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).

  As an application of SOFC, a combined power generation facility including an SOFC and an internal combustion engine has been proposed. In this combined power generation facility, the off-gas of the SOFC 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 to preheat the reformer and the SOFC. A device that devised this preheating control to enable early power generation at start-up has also been proposed (see, for example, Patent Document 1).

JP 2011-159585 A

  A fuel cell system capable of quick start-up by improving such a fuel cell system is desired, and a fuel cell system capable of efficient operation that can further save fuel consumption while interest in energy saving increases. Was demanded.

  Therefore, an object of the present invention is to provide a fuel cell system that enables quick start-up and efficient operation control.

  In order to achieve the above object, a fuel cell system according to the present invention includes a solid oxide fuel cell having a fuel electrode to which fuel gas is supplied and an air electrode to which air is supplied, and a generator provided separately therefrom. A reformer that reforms a fuel gas containing a hydrocarbon compound and supplies it to a fuel electrode of a solid oxide fuel cell, and an internal combustion engine that drives a generator. And an internal combustion engine capable of heating the solid oxide fuel cell with the exhaust gas discharged from the internal combustion engine, and a control means for controlling the supply of fuel to the internal combustion engine. A first port through which fuel and air can be introduced from the outside without passing through the solid oxide fuel cell is provided separately from the first port, and exhaust gas from the fuel electrode of the fuel cell is introduced into the internal combustion engine. Has a second port.

  In the present invention configured as described above, fuel and air can be supplied to the internal combustion engine flexibly according to the situation. As a result, quick start-up and efficient operation control are possible.

  In the present invention, preferably, the control means controls the opening and closing of the first port and the opening and closing of the second port independently. In the present invention configured as described above, fuel and air can be supplied to the internal combustion engine flexibly according to the situation.

  In the present invention, preferably, the control means closes the second port until the temperature of the solid oxide fuel cell reaches the complete warm-up temperature, opens and closes the first port, and supplies fuel and air from the outside. The internal combustion engine is operated by introducing it, the solid oxide fuel cell is preheated with the exhaust gas, and after the fuel cell reaches the complete warm-up temperature, the first port and the second port are opened / closed to open / close the internal combustion engine. Activate. In the present invention configured as described above, quick start-up becomes possible.

  Preferably, in the present invention, the control means is configured such that, after the temperature of the solid oxide fuel cell becomes equal to or higher than the fully warmed-up temperature, the fuel electrode side of the solid oxide fuel cell from the second port as fuel for the internal combustion engine. The gas that has passed through is introduced, air is introduced from the first port without introducing fuel, and the internal combustion engine is operated. In the present invention configured as described above, efficient operation control is possible.

  The fuel cell system of the present invention further includes an acquisition unit that acquires the composition information of the exhaust gas from the internal combustion engine, and the air introduced from the first port according to the composition information of the exhaust gas acquired by the acquisition unit. Adjust the amount. In this invention comprised in this way, incomplete combustion can be prevented and efficient combustion can be performed.

  Further, the fuel cell system of the present invention has an exhaust gas control means for controlling the route of the exhaust gas from the internal combustion engine, and the exhaust gas control means has a temperature of the solid oxide fuel cell that is lower than the complete warm-up temperature. In this case, exhaust gas is introduced into the solid oxide fuel cell. In the present invention configured as described above, quick start-up becomes possible.

  In the present invention, preferably, the exhaust gas is introduced into the reformer after the temperature of the solid oxide fuel cell becomes equal to or higher than the complete warm-up temperature. In the present invention configured as described above, quick start-up and efficient operation are possible.

  In the present invention, preferably, the first port and the second port are opened and closed by a continuously variable valve mechanism. In the present invention configured as described above, the pumping loss can be reduced, and efficient operation control can be performed.

  Preferably, in the present invention, the control means is configured such that after the temperature of the solid oxide fuel cell becomes equal to or higher than the complete warm-up temperature, the fuel electrode of the solid oxide fuel cell is connected from the second port in the combustion cycle of the internal combustion engine. After the gas passing through the side is introduced, the second port is closed and air is introduced from the first port. In the present invention configured as described above, efficient operation control and safe and stable operation are possible.

  According to the fuel cell system of the present invention, quick start-up and efficient operation control are possible.

It is the schematic which shows the basic composition of the fuel cell system by each embodiment of this invention. It is a perspective view which shows each port of the engine 3 of the fuel cell system by each embodiment of this invention. It is a block diagram which shows the input-output relationship of the control unit of the fuel cell system by each embodiment of this invention. It is a flowchart figure which shows the basic control of the fuel cell system by each embodiment of this invention. It is a flowchart figure which shows the control at the time of starting of the fuel cell system by each embodiment of this invention. It is the schematic which shows the operation | movement of the valve of each port in the engine independent operation mode of the fuel cell system by each embodiment of this invention. It is the schematic which shows the operation | movement of the valve of each port in the engine SOFC cooperation mode of the fuel cell system by the 1st Embodiment of this invention. It is the schematic which shows the operation | movement of the valve of each port in the engine SOFC cooperation mode of the fuel cell system by the 2nd Embodiment of this invention.

  As shown in FIG. 1, the fuel cell system according to the first embodiment of the present invention is a power source for driving an electric vehicle. During operation, the fuel cell system reforms a fuel gas containing a hydrocarbon compound to generate hydrogen gas. A reformer 1 to be generated, a solid oxide fuel cell (SOFC) 2 to which hydrogen gas generated by the reformer 1 is supplied, and a fuel supply passage for supplying fuel to the fuel electrode (anode) side of the SOFC 2 10b and an air supply passage 11a for supplying air to the air electrode (cathode) side of the SOFC2. Further, the engine 3 is provided as an internal combustion engine that sucks off-gas discharged from the SOFC 2 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 are provided. And the control means 5 (it mentions later with reference to FIG. 3) which controls the exhaust path control valves 4a and 4b is 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 this embodiment, liquefied natural gas (Liquid Petroleum gas: LPG) is used as the fuel gas. For example, when propane (C ₃ H ₈ ) in LPG reacts with water vapor, hydrogen, carbon monoxide, and carbon dioxide are generated. The fuel gas contains these components and also includes propane that has not reacted.

  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, a path of hydrogen gas and unreformed fuel gas supplied from the reformer 1 to the SOFC 2, that is, a fuel supply passage is indicated by a solid line 10 b, and a path of air supplied to the SOFC 2, that is, an air supply path is shown. This 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 through the fuel supply passage 10b. Air is supplied to the air electrode 22 through the air supply passage 11a.

  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. A catalyst containing nickel is used for the fuel electrode 21.

  The SOFC according to the present invention performs a power generation reaction at an operating temperature of about 650 ° C. 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. A state where the SOFC performs stable power generation in a high temperature state is called steady operation of the fuel cell system.

  The off-gas discharged from the fuel electrode 21 side of the SOFC 2 passes through a heat exchange mechanism (not shown) of the reformer 1, passes through an off-gas discharge passage 10 c indicated by a solid line, and a second port 32 of the engine 3 described later. Supplied to. In the present embodiment, both the gas (including unreacted fuel 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 separate off-paths. The A path of air supplied from the air electrode 22 to the engine 3 is indicated by a broken line 11b. The gas discharged from the air electrode 22 side is supplied to a first port 31 of the engine 3 to be described later.

  Since the operating temperature of the SOFC 2 is high, the off-gas discharged from the fuel electrode 21 of the SOFC 2 is usually as high as several hundred degrees Celsius. The off-gas discharged from the fuel electrode 21 of the SOFC 2 is guided to the reformer 1 through the off-gas passage 10c, and is heat-exchanged with the reformer 1 in a heat exchange mechanism (not shown) of the reformer 1, and reformed. Used to heat the vessel 1. In this way, the reformer 1 is heated while the off-gas is cooled, and then the cooled off-gas is supplied to the engine 3. Further, in order to realize an efficient engine, it is preferable to set the operating temperature of the SOFC 2 higher than the operating temperature of the reformer 1 in order to effectively use the exhaust heat of off-gas. In order to keep the temperature of the reformer 1 at a high temperature, it can be used in combination with the use of exhaust gas from the engine 3 described later, but the operating temperature of the SOFC 2 is set higher than the operating temperature of the reformer 1. Thus, since the temperature of the reformer 1 can be maintained centering on the off-gas of the SOFC 2, fuel burned by the engine 3 can be saved.

  The engine 3 of the present invention uses a multiport type engine from a conventionally known internal combustion engine having an intake / exhaust cycle. The engine 3 shown in FIG. 1 is a reciprocating engine having a first port 31 for intake, a second port 32 for intake, a third port 33 for exhaust, and a fourth port 34 for exhaust. Fuel (LPG) and air (Air) are supplied to the first port together with off-gas from the air electrode 22 side of the SOFC 2. The fuel and air are introduced from the outside through the air control valve 4d and the fuel control valve 4e, respectively. Since the air control valve 4d and the fuel control valve 4e are relatively close to the engine 3, there is an advantage that the response to the valve control is quicker than the off-gas passing through the SOFC 2. Off gas from the fuel electrode 21 side of the SOFC 2 is supplied to the second port. As will be described later, when the engine 3 is driven as an internal combustion engine, combustion in the engine 3 is optimized during normal operation. Therefore, the first port 31 of the engine 3 is connected to the SOFC 2 from the air electrode side. Air (Air) is supplied together with the off gas, and off gas from the fuel electrode 21 side of the SOFC 2 is supplied to the second port 32. It should be noted that during normal operation, fuel is basically not supplied to the first port 31 from the outside via the fuel control valve 4e.

  These ports of the engine 3 are opened and closed by port control valves, that is, valves. The first port 31 and the second port 32 are independently controlled to open and close by the first port valve 4f and the second port valve 4g. On the other hand, the two ports 33 and 34 for exhaust need not be controlled independently of each other but may be controlled as a common valve. The first port valve 4f and the second port valve 4g preferably use a continuously variable valve mechanism (not shown). By using such a continuously variable valve mechanism, the pumping loss (intake and exhaust loss) can be reduced, and for example, when the on / off control of the opening / closing operation of the second port is performed, it is performed within the control range of the continuously variable valve mechanism. There is an advantage that no special design is required.

  FIG. 1 is a schematic diagram showing the concept of the system. When the cut surface is viewed from the side of an actual engine, the first to fourth ports are not arranged as shown in FIG. The actual arrangement of each port is shown in FIG. As described above, the engine 3 has the first port 31 for intake, the second port 32 for intake, the third port 33 for exhaust, and the fourth port 34 for exhaust. The same thing as a valve engine can be adopted. The first port 31 and the second port 32 are independently controlled by the first port valve 4f and the second port valve 4g.

  The engine 3 is not a driving source for running the vehicle, and the connecting rod 36 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. Further, the piston 35 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, unreacted hydrogen contained in the off gas can be burned, and unreformed hydrocarbon compounds contained in the off gas can also be burned. Thus, by burning off-gas in the engine 3, it is possible to avoid releasing highly flammable hydrogen gas into the atmosphere, and to reduce the amount of unreacted hydrocarbon compounds in the off-gas, thereby reducing the amount of exhaust gas. Purification can be achieved.

  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 on the fuel electrode 21 side from the second port 32 in the intake cycle during normal operation. On the other hand, the off-gas on the air electrode 22 side may be sucked from the first port 31 and may be discharged without being supplied to the engine 3. As a result, fuel gas or the like is sucked from the reformer 1 at the fuel electrode 21 of the SOFC 2, and further fuel gas is sucked at the reformer 1. Therefore, the fuel cell unit according to the present embodiment does not require a blower for sending fuel gas to the reformer 1 and the SOFC 2 and a blower for sending air to the SOFC 2.

  The engine 3 burns fuel and then exhausts exhaust gas having a high temperature of several hundred degrees Celsius from the exhaust ports 33 and 34. 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.

  The control means is provided as the control unit 5. FIG. 3 is a block diagram showing the input / output relationship of the control unit 5. As shown in FIG. 3, 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 (State of Charge). : SOC) 55, SOFC temperature 56, and reformer temperature 57 are input. Information on the exhaust gas composition 58 from the engine 3 is also input. The exhaust gas composition 58 is used for grasping the combustion state of the engine 3 and used for controlling the supply of fuel and air, which will be described later. These pieces of information are detected by sensors (not shown). For example, the information on the exhaust gas composition 58 is acquired by an exhaust gas composition sensor (not shown).

  The control unit 5 controls the opening and closing of the exhaust path control valves 4a and 4b described above. The details of the method of controlling the exhaust path control valves 4a and 4b during steady operation are disclosed in Japanese Patent Application No. 2010-22358 already filed by the applicant, and this is also incorporated herein. .

  The control unit 5 opens and closes the fuel cell fuel control valve 4c that controls the amount of fuel gas supplied to the reformer 1, and air control that controls the amount of air and fuel supplied to the engine 3 separately from off-gas. The opening and closing of the valve 4d and the fuel control valve 4e are controlled. The control unit 5 also controls the opening and closing of the valves in the other fuel cell units, and further 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 degree of the air control valve 4d is adjusted in order to realize efficient combustion while monitoring the exhaust gas composition so as not to cause incomplete combustion. By realizing efficient combustion in this way, it becomes possible to clear regulations regarding exhaust gas particularly in the automobile field.

  Here, the fuel control valve 4e is basically closed during the steady operation. The fuel combusted in the engine 3 is reformed under the control of the fuel cell fuel control valve 4c, and the off-gas of the fuel gas supplied to the SOFC 2 is used. Compared with normal LPG, it is possible to operate efficiently by burning off-gas containing hydrogen, carbon monoxide, methane, or the like as fuel. 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. 5, the operation at the time of starting the fuel cell system by the control unit 5 will be described. First, the control unit 5 determines whether or not the SOFC 2 is in a cold state based on the information of the SOFC temperature 56 (S41). The cold state refers to a state where the temperature of the SOFC 2 is lower than the complete warm-up temperature. The complete warm-up temperature means the operating temperature during steady operation of the SOFC2. Here, when it is determined that the vehicle is not in the cold state, that is, since the steady operation is possible, the control unit 5 proceeds to a process for performing the steady operation (in the case of “No” in S41). If it is determined that the vehicle is in the cold state, the process proceeds to the next process for preheating (in the case of “Yes” in S41).

  When the control unit 5 determines that the engine is in the cold state, the control unit 5 first closes and stops the second port valve 4g and seals the SOFC off-gas line in preparation for engine operation for preheating. Then, the first port valve 4f is operated, and the air control valve 4d and the fuel control valve 4e are opened together to introduce air and fuel into the engine 3 (S43). By introducing the fuel gas into the engine 3 without passing through the reformer 1 and the SOFC 2, it is not necessary to pass a relatively cool fuel through the reformer 1 and the SOFC 2 that are subject to preheating, Efficient preheating can be performed.

  Next, in order to perform preheating, the control unit 5 operates the engine 3 and starts power generation. At this time, the control unit 5 controls the exhaust path control valves 4a and 4b, and uses the high-temperature exhaust gas generated with the operation of the engine 3 for preheating the reformer 1 and the SOFC 2 (S42).

  Since only the engine 3 is operating at this time, this state is referred to as an engine single operation mode. FIG. 6 shows a diagram relating to valve control in the engine single operation mode. The horizontal axis indicates time, and the vertical axis indicates the lift amount of each port valve during the intake cycle of the engine 3. A solid line I indicates a valve that opens and closes the first port 31, and a broken line II indicates a valve that opens and closes the second port 32. In this mode, the valve of the first port 31 is used, while the valve of the second port 32 is stopped, so that the graph is a flat straight line.

  Next, the control unit 5 determines whether or not the temperature Ts of the SOFC 2 has become equal to or higher than the complete warm-up temperature T1 based on the information on the SOFC temperature 56 (S44). Here, the complete warm-up temperature T1 is the operating temperature during steady operation of the SOFC2. When the temperature Ts is lower than the complete warm-up temperature T1, the control unit 5 continues the warm-up operation for preheating (in the case of “No” in S44). When the temperature Ts is equal to or higher than the complete warm-up temperature T1, the control unit 5 proceeds to a step for starting the operation of the SOFC 2 (in the case of “Yes” in S44).

  When the temperature Ts is equal to or higher than the complete warm-up temperature T1, or when the SOFC 2 is not in the cold state, the control unit 5 operates the engine 3 and starts the operation of the SOFC 2. Here, the control unit 5 controls the exhaust path control valves 4 a and 4 b so as to input the exhaust gas of the engine 3 mainly for preheating the reformer 1. In addition, the control unit 5 controls the fuel cell fuel control valve 4c and starts the operation of the second port 32 of the engine 3 so that it can be opened and closed. As a result, the off-gas on the fuel electrode 21 side of the SOFC 2 can be introduced into the engine 3. Further, the operation of the first port is continued so that the off-gas on the air electrode 22 side of the SOFC 2 is also introduced into the engine 3. In this way, the operation of the SOFC 2 is started (S45). The preheating by control of these exhaust paths can apply what was disclosed by Unexamined-Japanese-Patent No. 2011-159585.

  The control unit 5 preheats when starting the SOFC 2 and then switches the operation mode of the fuel cell system to the engine SOFC cooperation mode to continue the power generation operation. In this engine SOFC cooperation mode, the off-gas of SOFC 2 is introduced into the engine 3 and burned, thereby improving the efficiency and purifying the exhaust gas.

  FIG. 7 shows a diagram relating to valve control in the engine SOFC cooperation mode. Similar to FIG. 6, the horizontal axis represents time, and the vertical axis represents the valve lift amount of each port during the intake cycle of the engine 3. A solid line III indicates a valve that controls opening and closing of the first port 31, and a broken line IV indicates a valve that controls opening and closing of the second port 32. Unlike FIG. 6, it can be seen that both the valve of the first port 31 and the valve of the second port 32 are opening and closing. Note that the solid line and the dotted line are slightly shifted in the left-right direction for easy viewing, but actually operate at the same timing.

  According to the first embodiment, the fuel cell system can be started quickly and can be operated efficiently.

  A second embodiment of the present invention will be described. Although the configuration and main control flow of the second embodiment are the same as those of the first embodiment, the second embodiment differs from the first embodiment in the control of the intake port in the engine SOFC cooperation mode. Yes.

  In this fuel cell system, an oxygen-containing gas such as air and off-gas on the SOFC 2 air electrode 21 side flows on the first port side, whereas an off-gas containing hydrogen on the SOFC 2 fuel electrode 22 side on the second port side. Flows. In the second embodiment, the off gas on the fuel electrode 22 side of the SOFC 2 is first introduced into the engine 3 from the second port 32, and after the second port 32 is closed, the first port 31 is opened to contain oxygen. Introduce gas.

  FIG. 8 shows a valve control diagram regarding this operation. Similar to FIGS. 6 and 7, the horizontal axis represents time, and the vertical axis represents the valve lift amount of each port during the intake cycle of the engine 3. A solid line V indicates a valve that controls opening and closing of the first port 31, and a broken line VI indicates a valve that controls opening and closing of the second port 32. First, as indicated by the broken line VI, the valve of the second port 32 is opened, and after the off gas on the fuel electrode 22 side of the SOFC 2 is introduced into the engine 3, the valve is closed. Subsequently, as indicated by a solid line V, the valve of the first port 31 is opened, and a gas containing oxygen is introduced into the engine 3.

  In fact, the operating temperature of SOFC 2 during steady operation may reach 600 to 700 ° C., and hydrogen introduced from such a high temperature condition is expected to be in a high temperature state. By enabling the first port and the second port to operate independently and controlling as described above, the oxygen is introduced into the second port because the second port is closed when oxygen is introduced from the first port side. By reacting with the hot gas on the side, the gas flow path on the second port side can be prevented from burning backward. According to the second embodiment, in addition to the advantages of the first embodiment, safe and stable operation is possible. Such control is made possible by providing two intake ports for the engine 3 so that each can be controlled independently.

  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 4f First port valve 4g Second port valve 5 Control unit 6 Motor / generator 10b Fuel supply passage 10c Off gas discharge passage 11a Air supply passage 21 Fuel electrode (anode)
22 Air electrode (cathode)
31 1st port 32 2nd port 33, 34 Exhaust port 35 Cylinder 36 Connecting rod

Claims (9)

In a fuel cell system comprising a solid oxide fuel cell having a fuel electrode to which fuel gas is supplied and an air electrode to which air is supplied, and a generator provided separately from the fuel cell system,
A reformer for reforming a fuel gas containing a hydrocarbon compound and supplying the reformed fuel gas to the fuel electrode of the solid oxide fuel cell;
An internal combustion engine that drives the generator, the internal combustion engine capable of heating the solid oxide fuel cell with exhaust gas discharged from the internal combustion engine;
Control means for controlling the supply of fuel to the internal combustion engine,
The internal combustion engine has a first port through which fuel and air can be introduced into the internal combustion engine from the outside without passing through the solid oxide fuel cell;
A fuel cell system having a second port that is provided separately from the first port and introduces exhaust gas from the fuel electrode of the fuel cell into the internal combustion engine.   2. The fuel cell system according to claim 1, wherein the control unit independently controls opening and closing of the first port and opening and closing of the second port.   The control means closes the second port until the temperature of the solid oxide fuel cell reaches a complete warm-up temperature, opens and closes the first port, and introduces fuel and air from the outside. The internal combustion engine is operated, and the solid oxide fuel cell is preheated with the exhaust gas. After the solid oxide fuel cell reaches a complete warm-up temperature, the first port and the second port are The fuel cell system according to claim 2, wherein the internal combustion engine is operated by being opened and closed.   The control means passes the fuel electrode side of the solid oxide fuel cell from the second port as the fuel of the internal combustion engine after the temperature of the solid oxide fuel cell becomes equal to or higher than the complete warm-up temperature. The fuel cell system according to claim 2 or 3, wherein gas is introduced and air is introduced from the first port without introducing fuel to operate the internal combustion engine. The fuel cell system further includes
An acquisition means for acquiring composition information of the exhaust gas from the internal combustion engine is provided, and the amount of air introduced from the first port is adjusted according to the composition information of the exhaust gas acquired by the acquisition means. 5. The fuel cell system according to 4.   The fuel cell system has an exhaust gas control means for controlling a path of exhaust gas from the internal combustion engine, and the exhaust gas control means is provided when the temperature of the solid oxide fuel cell is lower than a complete warm-up temperature. The fuel cell system according to any one of claims 1 to 5, wherein exhaust gas is introduced into the fuel cell.   The fuel cell system according to claim 6, wherein the exhaust gas control means introduces the exhaust gas into the reformer after the temperature of the solid oxide fuel cell becomes equal to or higher than a complete warm-up temperature.   The fuel cell system according to any one of claims 2 to 7, wherein the first port and the second port are opened and closed by a continuously variable valve mechanism.   After the temperature of the solid oxide fuel cell becomes equal to or higher than the complete warm-up temperature, the control means moves the fuel electrode side of the solid oxide fuel cell from the second port in the combustion cycle of the internal combustion engine. The fuel cell system according to any one of claims 2 to 8, wherein after the gas that has passed is introduced, the second port is closed and air is introduced from the first port.

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