JP2007048490A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of using combustible component of anode off-gas in many ways. <P>SOLUTION: The fuel cell system (100) is provided with a fuel cell (40) and a separation means (50) separating the anode off-gas of the fuel cell (40) into first gas containing first combustible component and second gas containing second combustible component, accordingly, the combustible component of the anode off-gas can be used in many ways. As a result, combustion heat control or temperature control using the anode off-gas becomes possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a reformer.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. This fuel cell is environmentally superior and can realize high energy efficiency, and therefore has been widely developed as a future energy supply system.

  Currently, in many fuel cells, a reformer generates hydrogen-containing reformed gas from a hydrocarbon-based fuel such as gasoline, natural gas, and methanol, and supplies the reformed gas to the anode of the fuel cell. In this reformer, reforming is performed by a steam reforming reaction using steam or the like.

  Since this reforming reaction is an endothermic reaction, it is necessary to heat the reformer to promote the reforming reaction. Therefore, a fuel cell system in which heat is applied to the reformer by a combustion device or the like has been developed. For example, a technique using an anode off gas as a combustion gas for heating the reformer is disclosed (see, for example, Patent Document 1). According to this technique, high reforming efficiency can be obtained.

JP 2005-026059 A

  However, the technique of Patent Document 1 does not properly use combustible components in the anode off gas. In this case, the ignitability and combustion heat of the combustible components in the anode off-gas are different, so that the temperature in the reformer may become uneven. Therefore, the reforming efficiency may be reduced.

  An object of the present invention is to provide a fuel cell system in which combustible components in anode off-gas can be properly used.

  A fuel cell system according to the present invention separates a fuel cell and an anode off gas of the fuel cell into at least a first gas containing a first combustible component and a second gas containing a second combustible component. And separating means. In the fuel cell system according to the present invention, the anode off-gas is separated into the first gas containing at least the first combustible component and the second gas containing the second combustible component by the separating means. In this case, the combustible component in the anode off gas can be properly used. Therefore, combustion heat control using the anode off gas or temperature control using the anode off gas is possible.

  The amount of combustion heat of the first combustible component may be different from the amount of combustion heat of the second combustible component. In this case, it is possible to selectively use combustible components having different amounts of combustion heat. Therefore, combustion heat can be controlled using the first combustible component and the second combustible component. The first combustible component may be a hydrocarbon, and the second combustible component may be hydrogen. The hydrocarbon may be methane.

  Reforming means for generating reformed gas containing hydrogen from hydrocarbon fuel and supplying the reformed gas to the anode of the fuel cell, and reforming by burning at least one of the first combustible component and the second combustible component A combustion means for heating the quality means, a supply means for selecting one or both of the first gas and the second gas to supply to the combustion means, and controlling the supply means based on the required heat quantity of the reforming means And a control means for performing the above. In this case, the reforming gas is supplied to the anode of the fuel cell by the reforming means, and the reforming means is heated by reforming at least one of the first combustible component and the second combustible component in the combustion means, and reforming is performed. One or both of the first gas and the second gas are selectively supplied to the combustion means by the supply means based on the required heat quantity of the means. Thereby, the combustion heat in the combustion means is controlled by the combination of the first combustible component and the second combustible component. Therefore, the temperature of the reforming unit is controlled by the combination of the first combustible component and the second combustible component. Further, since the ignitability of the first combustible component and the second combustible component is different, the temperature distribution in the reforming section can be controlled. Therefore, the temperature of the reforming unit is efficiently and appropriately controlled. Further, when the hydrocarbon is methane, the heat of combustion in the combustion section is increased by increasing the ratio of methane. Thereby, the temperature of the reforming means can be increased efficiently.

  The supply means may adjust the flow rates of the first gas and the second gas to supply the first gas and the second gas to the combustion means. In this case, the flow rate of the first combustible component and the flow rate of the second combustible component supplied to the combustion means are adjusted. As a result, the temperature of the reforming means is more appropriately controlled.

  When the temperature of the reforming unit is raised, the control unit may control the supply unit so that the hydrocarbon ratio becomes large. Further, a required load detecting means for detecting a load required for the fuel cell may be further provided, and the control means may set the target temperature based on a detection result of the required load detecting means.

  The control means may control the supply means so that the second combustible component is supplied to the combustion means when starting the fuel cell. In this case, since the ignitability of the second combustible component is high, the reforming means can be efficiently heated. Further, the control means may control the supply means so that the first combustible component is supplied to the combustion means after the second combustible component is ignited. In this case, the temperature of the reforming means can be increased efficiently.

  According to the present invention, it is possible to properly use combustible components in the anode off gas. Therefore, combustion heat control using the anode off gas or temperature control using the anode off gas is possible.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic diagram showing an overall configuration of a fuel cell system 100 according to a first embodiment of the present invention. As shown in FIG. 1, the fuel cell system 100 includes a control unit 10, a fuel supply unit 20, a reformer 30, a fuel cell 40, a hydrogen separator 50, flow rate adjusting valves 60 and 61, air pumps 70 and 80, and required loads. A detection unit 90 is provided.

  The reformer 30 includes a reforming unit 31, a combustion unit 32, temperature sensors 33 and 34, and an excess air ratio λ sensor 35. The temperature sensor 33 is provided at the upstream end in the reforming unit 31. The temperature sensor 34 is provided at the downstream end in the reforming unit 31. The excess air ratio λ sensor 35 is provided in an exhaust system communicating from the combustion unit 32 to the outside. Here, the excess air ratio λ indicates the ratio of the amount of oxygen supplied to the combustion unit 32 to the amount of oxygen necessary for complete combustion in the combustion unit 32. The fuel cell 40 includes a cathode 41, an anode 42, a heat exchange unit 43, a voltmeter 44 and an ammeter 45. The hydrogen separator 50 has a structure partitioned into an anode offgas chamber 52 and a hydrogen chamber 53 by a hydrogen separation membrane 51.

  In this example, a hydrogen separation membrane battery was used as the fuel cell 40. Here, the hydrogen separation membrane battery is a fuel cell provided with a hydrogen separation membrane layer. The hydrogen separation membrane layer is a layer formed of a metal having hydrogen permeability. The hydrogen separation membrane battery has a structure in which the hydrogen separation membrane layer and an electrolyte having proton conductivity are laminated. Hydrogen supplied to the anode of the hydrogen separation membrane battery is converted into protons via the catalyst, moves through the proton conductive electrolyte, and combines with oxygen at the cathode to become water.

  The control unit 10 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and includes temperature sensors 33 and 34, excess air ratio λ sensor 35, voltmeter 44, ammeter. 45 and the fuel cell system 100 are controlled based on the detection results given from the required load detector 90. Details will be described later.

  The fuel supply unit 20 includes a storage unit that stores hydrocarbon fuel and a fuel supply unit such as an injector, and supplies a required amount of hydrocarbon fuel to the reforming unit 31 in accordance with instructions from the control unit 10. In this example, CNG (Compressed Natural Gas) was used as the hydrocarbon fuel. A hydrocarbon fuel other than CNG can be used as the hydrocarbon fuel.

  In the reforming unit 31, a reformed gas containing hydrogen is generated from a hydrocarbon fuel and a cathode off gas described later. First, a steam reforming reaction is caused by methane in the hydrocarbon fuel and steam in the cathode offgas, and hydrogen and carbon monoxide are generated. Next, a part of the generated carbon monoxide reacts with the water vapor in the cathode offgas, and hydrogen and carbon dioxide are generated. When the steam required for the steam reforming reaction is insufficient, oxygen and methane in the cathode offgas undergo a partial oxidation reaction, and hydrogen and carbon monoxide are generated.

  The reformed gas generated in the reforming unit 31 is supplied to the anode 42. At the anode 42, hydrogen in the reformed gas is converted into hydrogen ions. Hydrogen that has not been converted into hydrogen ions at the anode 42 and methane, carbon monoxide, nitrogen, and water vapor that have not reacted in the reforming unit 31 are supplied to the anode offgas chamber 52 of the hydrogen separator 50 as anode offgas. .

  Hydrogen in the anode off gas supplied to the anode off gas chamber 52 permeates the hydrogen separation membrane 51 and is supplied to the flow rate adjustment valve 61 through the hydrogen chamber 53. The flow rate adjustment valve 61 supplies a required amount of hydrogen to the combustion unit 32 in accordance with an instruction from the control unit 10. The anode off gas excluding hydrogen is supplied to the flow rate adjustment valve 60 without passing through the hydrogen separation membrane 51. The flow rate adjustment valve 60 supplies a required amount of anode off gas to the combustion unit 32 in accordance with instructions from the control unit 10.

  The air pump 70 supplies a necessary amount of air to the heat exchange unit 43 in accordance with an instruction from the control unit 10. The air supplied to the heat exchange unit 43 cools the fuel cell 40 and is supplied to the hydrogen chamber 53 of the hydrogen separator 50. The air supplied to the hydrogen chamber 53 purges the hydrogen that has permeated the hydrogen separation membrane 51 and is supplied to the combustion unit 32 through the flow rate adjustment valve 61 together with the purged hydrogen. Therefore, the hydrogen partial pressure in the hydrogen chamber 53 is maintained at a low value. As a result, the hydrogen in the anode off gas supplied to the anode off gas chamber 52 is efficiently separated by the hydrogen separation membrane 51.

  In the combustion unit 32, a combustion reaction occurs due to methane supplied from the flow rate adjustment valve 60, air and hydrogen supplied from the flow rate adjustment valve 61. Exhaust gas generated by the combustion reaction in the combustion unit 32 is discharged outside the fuel cell system 100. Further, the combustion heat generated by the combustion reaction in the combustion unit 32 is used for the steam reforming reaction in the reforming unit 31.

  The temperature sensor 33 detects the temperature of the upstream end in the reforming unit 31 and gives the detection result to the control unit 10. The temperature sensor 34 detects the temperature at the downstream end in the reforming unit 31 and gives the detection result to the control unit 10. The excess air ratio λ sensor 35 detects the excess air ratio λ in the combustion section 32 from the exhaust gas discharged from the combustion section 32 and gives the detection result to the control section 10.

  The air pump 80 supplies a necessary amount of oxygen to the cathode 41 in accordance with instructions from the control unit 10. In the cathode 41, water is generated and electric power is generated from hydrogen ions converted in the anode 42 and oxygen in the air supplied to the cathode 41. The generated water becomes water vapor by the heat generated in the fuel cell 40. Air that has not reacted with water vapor and hydrogen ions generated at the cathode 41 is supplied to the reforming unit 31 as cathode off-gas, and is used for the steam reforming reaction and the partial oxidation reaction, respectively.

  The voltmeter 44 detects the voltage generated by the power generation in the fuel cell 40 and gives the detection result to the control unit 10. The ammeter 45 detects a current generated by a power generation reaction in the fuel cell 40 and gives the detection result to the control unit 10. The required load detection unit 90 detects a load required for the fuel cell 40 (hereinafter referred to as a required load Preq), and gives the detection result to the control unit 10. The required load Preq is obtained from the accelerator opening, the output of the auxiliary machine, and the like.

  In the fuel cell system 100 according to the present embodiment, the amount of methane and the amount of hydrogen supplied to the combustion unit 32 can be adjusted. Thereby, the temperature and temperature distribution of the reforming unit 31 can be appropriately adjusted. Hereinafter, a method for controlling the molar ratio of hydrogen and methane supplied to the combustion unit 32 will be described.

  First, the control unit 10 estimates the molar ratio of hydrogen and methane supplied to the combustion unit 32 at the present time. Hereinafter, the ratio of the number of moles of methane to the number of moles of hydrogen is referred to as the mole ratio R. The molar ratio R in the combustion section 32 is estimated from the temperature of the catalyst provided in the reforming section 31 and the excess air ratio λ in the combustion section 32. The excess air ratio λ is detected by the excess air ratio λ sensor 35. The temperature of the catalyst of the reforming unit 31 is obtained by an average value (hereinafter, temperature average value Y) of a temperature detected by the temperature sensor 33 (hereinafter, temperature T1) and a temperature detected by the temperature sensor 34 (hereinafter, temperature T2). .

  The temperature average value Y includes the amount of heat necessary for the reforming reaction in the reforming section 31 (hereinafter referred to as the endothermic amount Q1), the amount of combustion heat in the combustion section 32 (hereinafter referred to as the combustion heat amount Q2), and the amount of heat released from the reformer 30 ( Hereinafter, it is determined by the heat dissipation amount Q3). Therefore, if the temperature average value Y, the heat absorption amount Q1, and the heat release amount Q3 are obtained, the combustion heat amount Q2 is obtained.

  The endothermic amount Q1 is the amount of hydrocarbon fuel supplied to the reforming unit 31 and the S / C ratio in the reforming unit 31 (the steam supplied to the reforming unit 31 and the hydrocarbon supplied to the reforming unit 31). (Molar ratio with carbon in fuel) and O / C ratio in reforming section 31 (molar ratio between oxygen supplied to reforming section 31 and carbon in hydrocarbon fuel supplied to reforming section 31) It is demanded from.

  The amount of hydrocarbon fuel supplied to the reforming unit 31 can be obtained from the control duty ratio of the injector of the fuel supply unit 20. The S / C ratio is obtained from the generated current of the fuel cell 40. Therefore, the S / C ratio can be obtained from the detection result of the ammeter 45. The O / C ratio is obtained from the generated current of the fuel cell 40 and the amount of oxygen supplied from the air pump 80 to the cathode 41. The amount of oxygen supplied from the air pump 80 to the cathode 41 can be obtained from the number of revolutions of the air pump 80, and can also be obtained by a flow meter.

  The amount of combustion heat Q2 can be obtained from the amount of fuel supplied to the combustion unit 32 and the excess air ratio λ. Hereinafter, the combustion heat quantity Q2 will be described. FIG. 2 is a diagram showing a relationship among the molar ratio R, the excess air ratio λ, and the combustion heat quantity Q2. The horizontal axis in FIG. 2 indicates the excess air ratio λ, and the vertical axis in FIG. 2 indicates the normalized combustion heat quantity. Here, the normalized combustion heat quantity represents a ratio to the combustion heat quantity Q2 when the molar ratio of hydrogen to methane is 1: 1 and the excess air ratio λ is 3.

  The combustion heat of hydrogen is 241.8 kJ / mol, and the combustion heat of methane is 802.4 kJ / mol, which is larger than the combustion heat of hydrogen. Therefore, as shown in FIG. 2, the combustion heat quantity Q2 increases as the molar ratio of methane increases. Further, the combustion heat quantity Q2 becomes maximum when the excess air ratio λ is 1, and decreases when the excess air ratio λ becomes larger than 1. It is because the combustible raw material used for combustion decreases. From the above, when the amount of combustion heat Q2 is obtained, the amount of fuel supplied to the combustion unit 32 is obtained based on FIG. Further, when the amount of fuel supplied to the combustion unit 32 is obtained, the molar ratio R is obtained. The amount of heat release Q3 depends on the structure, size, and the like of the reformer 30. From the above, the molar ratio R can be estimated if the temperature average value Y and the excess air ratio λ are detected.

  Next, the control unit 10 calculates a required amount of heating heat Qtrg that the combustion unit 32 needs to give to the reforming unit 31 when the fuel cell 40 outputs the required load Preq. Here, when the required load Preq increases, the amount of hydrogen necessary for power generation in the fuel cell 40 also increases. In order to increase the amount of hydrogen supplied to the fuel cell 40, it is necessary to promote the reforming reaction in the reforming unit 31. Since the reforming reaction is an endothermic reaction, it is necessary to increase the temperature of the reforming unit 31 in order to promote the reforming reaction. Therefore, the required heating heat quantity Qtrg is a function of the required load Preq. Hereinafter, the relationship between the required load Preq and the required heating heat quantity Qtrg will be described.

  FIG. 3 is a diagram showing the relationship between the required load Preq of the fuel cell 40 and the required heating heat quantity Qtrg. The horizontal axis in FIG. 3 indicates the required load Preq, and the vertical axis in FIG. 3 indicates the required heating heat quantity Qtrg. As shown in FIG. 3, the required heating heat quantity Qtrg is proportional to the required load Preq and increases as the required load Preq increases. From the above, the control unit 10 obtains the required heating heat quantity Qtrg from the required load Preq using FIG.

  Next, the control unit 10 obtains a heating heat amount Q (= combustion heat amount Q2-heat absorption amount Q1-heat dissipation amount Q3) given from the combustion unit 32 to the reforming unit 31. FIG. 4 is a diagram illustrating the relationship between the generated power W generated by the power generation reaction of the fuel cell 40 and the amount of heat Q. The horizontal axis in FIG. 4 indicates the generated power W, and the vertical axis in FIG. As shown in FIG. 4, the heating heat quantity Q is proportional to the generated power W, and increases as the generated power W increases. From the above, the control unit 10 obtains the heating heat quantity Q from the generated power W using FIG. Note that the amount of heating heat Q is corrected to increase as the heat release amount Q3 of the reformer 30 increases. Further, the control unit 10 calculates the generated power W based on the detection results of the voltmeter 44 and the ammeter 45.

  Here, the ignitability of hydrogen and methane will be described. Hydrogen has higher ignitability than methane and ignites as soon as it is supplied to the combustion section 32. Therefore, when hydrogen is supplied to the combustion unit 32, the temperature at the upstream end in the combustion unit 32 increases. Thereby, the temperature at the upstream end in the reforming section 31 increases. On the other hand, methane is less ignitable than hydrogen. Thereby, the time until the methane is ignited becomes longer. Therefore, when methane is supplied to the combustion unit 32, the temperature at the downstream end in the combustion unit 32 increases. As a result, the temperature at the downstream end in the reforming unit 31 increases. From the above, if the amounts of methane and hydrogen are not properly adjusted, a temperature distribution is generated in the reforming unit 31. In the present embodiment, the control unit 10 prevents the temperature distribution from occurring based on the molar ratio R. Details thereof will be described below.

  First, the control unit 10 determines whether or not the difference between the required heating heat quantity Qtrg and the heating heat quantity Q is large. If the difference between the required heating heat amount Qtrg and the heating heat amount Q is equal to or greater than the threshold value Qref, the control unit 10 determines that the temperature distribution is generated in the reforming unit 31 and corrects the molar ratio R. FIG. 5 is a map used when the control unit 10 corrects the molar ratio R. The horizontal axis in FIG. 5 indicates the difference between the temperature T2 and the temperature T1, and the vertical axis in FIG. 5 indicates the correction molar ratio Rtrg.

  As shown in FIG. 5, the control unit 10 sets the correction molar ratio Rtrg to a smaller value as the difference between the temperature T2 and the temperature T1 increases. When the corrected molar ratio Rtrg is obtained, the control unit 10 reflects the corrected molar ratio Rtrg in the current molar ratio R. As an example, the control unit 10 sets the average value of the current molar ratio R and the corrected molar ratio Rtrg to a new molar ratio R. Next, the control unit 10 controls the flow rate adjustment valves 60 and 61 based on the new molar ratio R. Note that the threshold value Qref is appropriately selected. The corrected molar ratio Rtrg is determined in consideration of the temperature change responsiveness due to the ignitability of hydrogen and methane. As described above, the correction of the molar ratio R prevents the temperature distribution in the combustion section 32 from occurring. As a result, the occurrence of temperature distribution in the reforming unit 31 is prevented.

  From the above, in the fuel cell system 100 according to the present embodiment, the temperature of the reforming unit 31 is efficiently controlled by adjusting the molar ratio R. Further, by adjusting the molar ratio, it is possible to prevent the temperature distribution of the reforming part 31 from occurring. Therefore, the reforming reaction in the reforming unit 31 is performed efficiently.

  Next, a flowchart when the control unit 10 controls the molar ratio R will be described. FIG. 6 is a diagram showing an example of the flowchart. The control unit 10 executes the flowchart of FIG. 6 at a predetermined cycle (for example, every 500 ms). As shown in FIG. 6, the control unit 10 estimates the molar ratio R from the excess air ratio λ and the temperature average value Y using FIG. 2 (step S1).

  Next, the control part 10 calculates | requires required heating calorie | heat amount Qtrg from the request | requirement load Preq using FIG. 3 (step S2). Subsequently, the control part 10 calculates | requires the heating-heat amount Q from the generated electric power W using FIG. 4 (step S3). Next, the control unit 10 determines whether or not the absolute value of the difference between the required heating heat amount Qtrg and the heating heat amount Q is less than the threshold value Qref (step S4).

  If it is not determined in step S4 that the absolute value of the difference between the required heating heat amount Qtrg and the heating heat amount Q is less than the threshold value Qref, the control unit 10 uses the map of FIG. The correction molar ratio Rtrg is calculated from the difference between the two (step S5). Next, the control unit 10 resets the average value of the molar ratio R estimated in step S1 and the corrected molar ratio Rtrg calculated in step S5 to a new molar ratio R (step S6).

  Next, the control unit 10 controls the flow rate adjusting valves 60 and 61 based on the molar ratio R set in step S6 (step S7). Thereafter, the control unit 10 ends the operation. If it is determined in step S4 that the absolute value of the difference between the required heating heat quantity Qtrg and the heating heat quantity Q is less than the threshold value Qref, the control unit 10 performs the operation of step S7.

  As described above, the molar ratio R is appropriately set by controlling the fuel cell system 100 according to the flowchart of FIG. Thereby, the reforming reaction in the reforming unit 31 is performed efficiently.

  In this embodiment, the hydrogen separation membrane battery is used as the fuel cell 40, but other fuel cells can be used. Further, a buffer tank may be provided between the hydrogen separator 50 and the flow rate adjusting valves 60 and 61. Furthermore, in the present embodiment, the temperature of the catalyst of the reforming unit 31 is obtained by both the temperature sensors 33 and 34, but can be obtained by either one. In this embodiment, both the flow rate of hydrogen and the flow rate of methane are controlled, but the molar ratio R can also be controlled by changing one of the flow rates. Further, the hydrogen separated by the hydrogen separator 50 may be used as a fuel gas supplied to the anode 42 of the fuel cell 40.

  In this embodiment, the reforming unit 31 corresponds to the reforming unit, the hydrogen separator 50 corresponds to the separating unit, the combustion unit 32 corresponds to the burning unit, and the flow rate adjusting valves 60 and 61 correspond to the supplying unit. The control unit 10 corresponds to the control unit, the required load detection unit 90 corresponds to the required load detection unit, and the required heating heat amount Qtrg corresponds to the required heat amount.

  Subsequently, a fuel cell system 100a according to a second embodiment of the present invention will be described. FIG. 7 is a schematic diagram showing the overall configuration of the fuel cell system 100a. The fuel cell system 100a is different from the fuel cell system 100 of FIG. 1 in that an ignition device 36 is provided in the reforming unit 31, a hydrogen storage / release device 54, a methane storage / release device 55, and a start switch 91 are newly provided. The point provided is that the switching valves 62 and 63 are provided instead of the flow rate adjusting valves 60 and 61.

  The start switch 91 is a switch for starting the fuel cell 40 and is operated by a user. The ignition device 36 ignites the hydrogen gas supplied to the reforming unit 31 according to an instruction from the control unit 10 when the fuel cell 40 is started. In this case, since the ignitability of hydrogen is high, the fuel cell 40 can be efficiently heated.

  The hydrogen storage / release device 54 includes a hydrogen storage alloy or the like. The hydrogen in the hydrogen chamber 53 is supplied to the hydrogen storage / release device 54. The hydrogen storage / release device 54 stores supplied hydrogen or releases a required amount of hydrogen in accordance with an instruction from the control unit 10. The hydrogen released by the hydrogen storage / release device 54 is supplied to the switching valve 62.

  The methane storage / release device 55 includes a hydrocarbon adsorbent and the like. The anode off gas in the anode off gas chamber 52 is supplied to the methane storage / release device 55. The methane storage / release device 55 stores methane in the supplied anode off-gas or releases a required amount of methane in accordance with an instruction from the control unit 10. The methane released by the methane storage / release device 55 is supplied to the switching valve 63.

  The switching valves 62 and 63 are formed of a three-way cock or the like. The switching valve 62 switches the supply of the hydrogen supplied from the hydrogen storage / release device 54 to the reforming unit 31 and the combustion unit 32 in accordance with an instruction from the control unit 10. The switching valve 63 switches the supply of methane supplied from the methane storage / release device 55 to the reforming unit 31 and the combustion unit 32 in accordance with an instruction from the control unit 10.

  In the fuel cell system 100a according to the present embodiment, the fuel cell 40 can be efficiently activated by adjusting the amount of methane and hydrogen supplied to the reforming unit 31. Thereby, the temperature and temperature distribution of the reforming unit 31 can be appropriately adjusted. A method for controlling the amount of hydrogen and the amount of methane supplied to the combustion unit 32 when the fuel cell 40 is started will be described.

  First, the control unit 10 controls the hydrogen storage / release device 54 and the switching valve 62 so that hydrogen is supplied to the reforming unit 31 when the start switch 91 is turned on. Next, the control unit 10 controls the ignition device 36 so that hydrogen is ignited in the reforming unit 31. Thereby, the temperature of the reforming unit 31 increases. Further, high-temperature combustion gas generated by hydrogen combustion is supplied to the anode 42. As a result, the fuel cell 40 is efficiently heated.

  After the hydrogen is ignited, the control unit 10 controls the hydrogen storage / release device 54 so that the amount of hydrogen supplied to the reforming unit 31 increases. When the temperature of the reforming unit 31 becomes equal to or higher than the ignition temperature of methane, the control unit 10 controls the methane storage / release device 55 and the switching valve 63 so that methane is supplied to the reforming unit 31. Thereafter, the control unit 10 controls the amount of hydrogen and methane supplied to the reforming unit 31 so that the temperature of the reforming unit 31 increases to an appropriate temperature. In this case, the control unit 10 follows the map of FIG.

  FIG. 8 is a map showing the amount of hydrogen and the amount of methane that need to be supplied to the reforming unit 31 after the ignition of hydrogen. The horizontal axis of FIG. 8 shows the temperature average value Y, and the vertical axis of FIG. As shown in FIG. 8, after hydrogen ignition, the amount of hydrogen supplied to the reforming unit 31 increases until the temperature average value Y increases to the ignition temperature of methane. Accordingly, the temperature of the reforming unit 31 can be increased efficiently, and the fuel cell 40 is heated by the combustion gas supplied to the anode 42.

  When the temperature of the reforming unit 31 becomes equal to or higher than the ignition temperature of methane, the amount of hydrogen supplied to the reforming unit 31 decreases and the amount of methane supplied to the reforming unit 31 increases. Here, the ignitability of methane is lower than that of hydrogen, but the heat of combustion of methane is greater than the heat of combustion of hydrogen. Therefore, the temperature of the reforming unit 31 can be further increased, and the temperature of the combustion gas supplied to the anode 42 is increased. As a result, the fuel cell 40 is heated more efficiently.

  When the temperatures of the reforming unit 31 and the fuel cell 40 are equal to or higher than the respective starting temperatures (for example, about 400 ° C.), the control unit 10 causes the fuel supply unit to supply hydrocarbon fuel and oxygen to the reforming unit 31. 20 and the air pump 80 are controlled. As a result, a partial oxidation reaction occurs in the reforming unit 31 and the reformed gas is supplied to the anode 42. As a result, power generation is performed in the fuel cell 40. In this case, the amount of water vapor contained in the cathode offgas increases and the amount of hydrogen contained in the anode offgas increases.

  Thereafter, the control unit 10 controls the hydrogen storage / release device 54 and the switching valve 62 so that the amount of hydrogen supplied to the combustion unit 32 increases. Thereby, the temperature of the reforming part 31 further increases. Further, the control unit 10 controls the air pump 80 so that the O / C ratio in the reforming unit 31 gradually decreases. In this case, the control unit 10 follows the map of FIG.

  FIG. 9 is a map showing the O / C ratio after the start of the partial oxidation reaction. The horizontal axis in FIG. 9 indicates the temperature average value Y, and the vertical axis in FIG. 9 indicates the O / C ratio in the reforming unit 31. As shown in FIG. 9, after the partial oxidation reaction starts, the O / C decreases as the temperature average value Y increases. Thereby, it becomes easy to shift to the steam reforming reaction.

  When the temperature of the reforming unit 31 becomes equal to or higher than the normal reforming temperature (for example, about 600 ° C.), the control unit 10 causes the fuel supply unit 20, the air pump 80, and the The switching valves 62 and 63 are controlled. The startup of the fuel cell 40 is completed by the above procedure.

  From the above, the fuel cell system 100a according to the present embodiment can efficiently control the temperature of the reforming unit 31. As a result, the fuel cell 40 can be started up efficiently.

  Next, a flowchart when the control unit 10 controls the fuel cell system 100a when the fuel cell 40 is activated will be described. FIG. 10 is a diagram showing an example of the flowchart. The control unit 10 executes the flowchart of FIG. 10 at a predetermined cycle (for example, every 500 ms). As shown in FIG. 10, the control unit 10 determines whether or not the activation switch has been turned on by the user (step S11).

  If it is not determined in step S11 that the start switch 91 has been turned on, the control unit 10 ends the operation. When it is determined in step S11 that the start switch 91 is turned on, the control unit 10 determines whether or not the temperature average value Y is lower than the hydrogen ignition temperature Tref1 (step S12). When it is determined in step S12 that the temperature average value Y is lower than the hydrogen ignition temperature Tref1, the control unit 10 controls the hydrogen storage / release device 54 and the switching valve 62 so that hydrogen is supplied to the reforming unit 31. (Step S13).

  Next, the control unit 10 controls the ignition device 36 so that the hydrogen supplied to the reforming unit 31 is ignited (step S14). Next, the control unit 10 determines whether or not hydrogen has ignited (step S15). In this case, the control unit 10 can determine whether or not the temperature T1 has increased.

  If it is not determined in step S15 that hydrogen has ignited, the control unit 10 repeats the operation in step S14. When it is determined in step S15 that hydrogen has ignited, the control unit 10 controls the hydrogen storage / release device 54 using the map of FIG. 8 so that the amount of hydrogen supplied to the reforming unit 31 increases (step S15). S16). When it is not determined in step S12 that the temperature average value Y is lower than the hydrogen ignition temperature Tref1, the control unit 10 performs the operation of step S16. Thereby, the hydrogen supplied to the reforming unit 31 is ignited.

  Next, the controller 10 determines whether or not the temperature average value Y is lower than the methane ignition temperature Tref2 (step S17). When it is determined in step S17 that the temperature average value Y is lower than the methane ignition temperature Tref2, the control unit 10 repeats the operation of step S16. If it is not determined in step S17 that the temperature average value Y is lower than the methane ignition temperature Tref2, the control unit 10 uses the map in FIG. 8 to generate hydrogen and methane so that hydrogen and methane are supplied to the reforming unit 31. The storage / release device 54, the methane storage / release device 55, and the switching valves 62 and 63 are controlled (step S18).

  Next, the control unit 10 determines whether or not the temperature average value Y is less than the reforming function start temperature Tref3 (step S19). In this embodiment, the reforming function start temperature Tref3 is set to 400 ° C. When it is determined in step S19 that the temperature average value Y is lower than the reforming function start temperature Tref3, the control unit 10 repeats the operation of step S18. When it is not determined in step S19 that the temperature average value Y is lower than the reforming function start temperature Tref3, the control unit 10 controls the air pump 80 so as to obtain a desired O / C ratio using the map of FIG. (Step S20).

  Next, the controller 10 determines whether or not the temperature average value Y is less than the normal reforming temperature Tref4 (step S21). In this embodiment, the normal reforming temperature Tref4 is set to 600 ° C. When it is determined in step S21 that the temperature average value Y is lower than the normal reforming temperature Tref4, the control unit 10 repeats the operation of step S20. When it is not determined in step S21 that the temperature average value Y is lower than the normal reforming temperature Tref4, the control unit 10 ends the operation. The startup of the fuel cell 40 is completed by the above procedure.

  As described above, the temperature of the reforming unit 31 can be efficiently controlled by performing the control according to the flowchart of FIG. As a result, the fuel cell 40 can be started up efficiently. In this embodiment, the reforming unit 31 corresponds to a reforming unit and a combustion unit.

  Subsequently, a fuel cell system 100b according to a third embodiment of the present invention will be described. FIG. 11 is a schematic diagram showing the overall configuration of the fuel cell system 100b. The fuel cell system 100 b is different from the fuel cell system 100 of FIG. 1 in that a CO storage / release device 56 is newly provided in the methane storage / release device 55. The CO storage / release device 56 has a structure including a CO adsorption material such as palladium, and stores or releases CO in the anode off-gas in accordance with instructions from the control unit 10.

  In the fuel cell system 100b according to the present embodiment, the methane stored in the methane storage / release device 55 and the CO stored in the CO storage / release device 56 are supplied to the combustion unit 32 by the switching valve 63, and are contained in the anode off-gas. Nitrogen and water vapor are discharged to the outside. Thereby, the exhaust gas flow rate from the combustion part 32 is reduced. Therefore, the heating efficiency of the reforming unit 31 by the combustion unit 32 is improved. As a result, the system efficiency of the fuel cell system 100b is improved.

1 is a schematic diagram showing an overall configuration of a fuel cell system according to a first embodiment of the present invention. It is a figure which shows the relationship between a molar ratio, an air excess rate, and a combustion heat amount. It is a figure which shows the relationship between the request | requirement load of a fuel cell, and required heating calorie | heat amount. It is a figure which shows the relationship between the electric power which generate | occur | produces by the electric power generation reaction of a fuel cell, and heating calorie | heat amount. It is a map used when a control part correct | amends molar ratio. It is a figure for demonstrating an example of the flowchart at the time of a control part controlling molar ratio. It is a schematic diagram which shows the whole structure of the fuel cell system which concerns on 2nd Example of this invention. It is a map which shows the amount of hydrogen and the amount of methane which need to be supplied to a reforming part after ignition of hydrogen. It is a map which shows O / C ratio after the partial oxidation reaction start. It is a figure for demonstrating an example of the flowchart at the time of a control part controlling a fuel cell system at the time of starting of a fuel cell. It is a schematic diagram which shows the whole structure of the fuel cell system which concerns on 3rd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control part 20 Fuel supply part 30 Reformer 31 Reformer part 32 Combustion part 33,34 Temperature sensor 35 Excess air ratio (lambda) sensor 36 Ignition apparatus 40 Fuel cell 50 Hydrogen separator 54 Hydrogen storage-release apparatus 55 Methane storage-release apparatus 60 , 61 Flow control valve 62, 63 Switching valve 90 Required load detector 91 Start switch 100, 100a, 100b Fuel cell system

Claims (10)

A fuel cell;
Separation means for separating the anode off-gas of the fuel cell into at least a first gas containing a first combustible component and a second gas containing a second combustible component. Battery system. 2. The fuel cell system according to claim 1, wherein the amount of combustion heat of the first combustible component is different from the amount of combustion heat of the second combustible component. The first combustible component is a hydrocarbon;
The fuel cell system according to claim 1 or 2, wherein the second combustible component is hydrogen. The fuel cell system according to claim 3, wherein the hydrocarbon is methane. Reforming means for generating a reformed gas containing hydrogen from a hydrocarbon fuel and supplying the reformed gas to the anode of the fuel cell;
Combustion means for heating the reforming means by burning at least one of the first combustible component and the second combustible component;
Supply means for selecting one or both of the first gas and the second gas and supplying the selected gas to the combustion means;
The fuel cell system according to any one of claims 1 to 4, further comprising a control unit that controls the supply unit based on a required heat amount of the reforming unit. The said supply means adjusts the flow volume of the said 1st gas and the said 2nd gas, The said 1st gas and the said 2nd gas are supplied to the said combustion means, It is characterized by the above-mentioned. Fuel cell system. 7. The fuel cell system according to claim 5, wherein, when the temperature of the reforming unit is increased, the control unit controls the supply unit so that the ratio of the hydrocarbon is increased. Further comprising required load detecting means for detecting a load required for the fuel cell;
8. The fuel cell system according to claim 5, wherein the control unit sets the required heat quantity based on a detection result of the required load detection unit. The control means controls the supply means so that the second combustible component is supplied to the combustion means when the fuel cell is started. The fuel cell system described. 10. The fuel cell according to claim 9, wherein the control means controls the supply means so that the first combustible component is supplied to the combustion means after the second combustible component is ignited. system.

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