JP5026009B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that supplies air at an appropriate flow rate to each of a combustion section and a fuel cell of a fuel processing apparatus with one air supply means.

A fuel cell generates electricity by an electrochemical reaction between hydrogen and oxygen. In general, air is supplied to the fuel cell, and oxygen in the air is used for power generation. On the other hand, the hydrogen used for power generation of the fuel cell is covered by using a fuel processing device that reforms the raw material into a gas rich in hydrogen and supplying the fuel-rich reformed gas generated by the fuel processing device to the fuel cell. There are many cases. When reforming a raw material in a fuel processing apparatus, reforming heat is supplied, but the reforming heat is generally generated by supplying fuel and air to the combustion section of the fuel processing apparatus and burning the fuel. Is. Conventionally, air has been individually supplied to the fuel cell and the combustion section of the fuel processing apparatus (see, for example, Patent Document 1).
JP 2006-49040 A (FIG. 1 etc.)

  If air can be supplied to the fuel cell and the combustion section of the fuel processing apparatus by a single air supply means, the cost can be reduced. However, since the ratio of the air supplied to the fuel cell and the combustion part of the fuel processing device is not necessarily constant, air of an appropriate flow rate is supplied to each of the fuel cell and the combustion part of the fuel processing device by one air supply means. It was difficult to supply.

  In view of the above-described problems, an object of the present invention is to provide a fuel cell system that supplies air at an appropriate flow rate to each of a combustion section of a fuel cell and a fuel processing device with one air supply means.

  In order to achieve the above object, a fuel cell system according to a first aspect of the present invention is a modified fuel cell system in which a raw material m1 is introduced and reformed to generate a reformed gas g rich in hydrogen, as shown in FIG. A fuel processor 20 having a mass part 25 and a combustion part 23 for introducing the fuel p and the combustion air a and combusting the fuel p to generate reforming heat used for reforming in the reforming part 25; A fuel cell 30 that introduces the power generation air t and the reformed gas g, and generates power by an electrochemical reaction between oxygen in the power generation air t and hydrogen in the reformed gas g; Supply means 42 for supplying power generation air t to the fuel cell 30; combustion air flow rate detection means 48 for detecting the flow rate of combustion air a introduced into the combustion section 23; Combustion air flow rate adjusting hand for adjusting the flow rate of the introduced combustion air a 42, 68GP; fuel flow grasping means 41, 43, 46 for grasping the flow rate of the fuel p introduced into the combustion section 23; the flow rate of oxygen in the combustion air a in the combustion section 23 in the fuel p And a control device 40 for controlling the combustion air flow rate adjusting means 42 and 68GP so that the ratio of the combustible component to the flow rate becomes a predetermined ratio.

  With this configuration, the air supply means for supplying the combustion air to the combustion section and the power generation air to the fuel cell is provided, so that the air is supplied to the combustion section of the fuel cell and the fuel processing device by one air supply means. Can be supplied. In addition, since the combustion air flow rate adjusting means is controlled so that the ratio of the flow rate of oxygen in the combustion air to the flow rate of combustible components in the fuel in the combustion section becomes a predetermined ratio, it is particularly suitable for the combustion section. A flow rate of combustion air can be supplied, and emission of carbon monoxide accompanying incomplete combustion of fuel can be reduced.

In addition, the fuel cell system according to the first aspect of the present invention includes, for example, as shown in FIG. 1, the combustion part 23 using, as fuel, anode offgas p containing hydrogen that has not been used for the electrochemical reaction in the fuel cell 30. An anode off-gas pipe 52 that leads to the fuel cell 30 ; a power generation air flow rate detection means 41 and 44 that detects the flow rate of the power generation air t introduced into the fuel cell 30; and a power generation current detection means 43 that detects the power generation current in the fuel cell 30 The control device 40 is configured to control the air supply means 42 so that the oxygen utilization rate in the fuel cell 30 becomes the first predetermined utilization rate.

  With this configuration, the air supply means is controlled so that the oxygen utilization rate in the fuel cell becomes the first predetermined utilization rate. Therefore, the low humidification operation is prevented by excessive air supply, and the air supply is insufficient. It is possible to prevent the power generation voltage from becoming unstable, and it is possible to adjust the supply flow rate of power generation air so as not to reduce the durability of the fuel cell. That is, it is possible to supply power generation air at an appropriate flow rate to the fuel cell.

The fuel cell system according to the first aspect of the present invention, for example, as shown in FIG. 1, the combustion air supply line 58 leading to the combustion air a discharged from air supply means 42 to the combustion section 23 A plurality of throttle means 68A, 68B having different pressure losses and a throttle means group 68GP arranged in parallel on the combustion air supply line 58; and the air supply means 42 generates air by rotation of the motor. The combustion air flow rate adjusting means is composed of a rotational speed adjusting means 42v for adjusting the rotational speed of the motor and a throttle means group 68GP; and the control device 40 is a combustion air in the combustion section 23. The oxygen utilization rate in the fuel cell 30 becomes the first predetermined utilization rate while adjusting the rotation speed of the motor so that the ratio of the flow rate of a to the flow rate of the fuel p becomes a predetermined air ratio. A plurality of throttling means 68A, throttle means 68A to flow combustion air a from the 68B to, is configured to determine 68B.

  With this configuration, a plurality of throttle means having different pressure losses are provided on the combustion air supply line, and the throttle means group is configured to be arranged in parallel, and the fuel flow rate of the combustion air flow rate in the combustion section The combustion air is allowed to flow from the plurality of throttle means so that the oxygen utilization rate in the fuel cell becomes the first predetermined utilization rate while adjusting the rotational speed of the motor so that the ratio to the air ratio becomes a predetermined air ratio. Since the throttling means is determined, air of an appropriate flow rate can be supplied to each of the combustion portions of the fuel cell and the fuel processing apparatus with a simple configuration.

Further, the fuel cell system according to the invention described in claim 3 is, for example, as shown in FIG. 1, for generating power discharged from the air supply means 42 in the fuel cell system 10 according to claim 1 or 2 . A power generation air supply line 54 for guiding the air t to the fuel cell 30; and a shutoff valve 64 disposed in the power generation air supply line 54 and capable of blocking the flow of the power generation air t in the power generation air supply line 54. Prepare.

  If comprised in this way, since the cutoff valve which can interrupt | block the flow of power generation air of a power generation air supply line is provided, it becomes possible to interrupt | block the flow of power generation air when not generating power, and does not generate power It is possible to prevent deterioration of the fuel cell performance due to the catalyst deterioration of the fuel cell and the membrane drying caused by supplying air to the fuel cell.

A fuel cell system according to a fourth aspect of the present invention is the combustion air in the fuel cell system according to any one of the first to third aspects, for example, referring to FIG. The flow rate detection means 48 is a flow meter.

  If comprised in this way, the flow volume of combustion air can be measured directly, it will become possible to adjust combustion air flow volume adjustment means with high precision, and incomplete combustion of fuel more reliably. The accompanying carbon monoxide emissions can be reduced.

The fuel cell system according to the invention of claim 5, for example, as shown in FIG. 1, in the fuel cell system 10 according to any one of claims 1 to 4, introduced into the fuel cell 30 A calculation unit 41 for determining the flow rate of the power generation air t from the pressure of the generated power generation air t; a pressure detector for detecting the pressure of the power generation air t introduced into the fuel cell 30 by the power generation air flow rate detection means 44 and the calculation part 41 are comprised.

  If comprised in this way, since the power generation air flow rate detection means is comprised including the pressure detector and operation part which detect the pressure of the power generation air introduce | transduced into a fuel cell, it is generally cheaper than a flowmeter. A pressure detector can be used, and the cost of the fuel cell system can be reduced.

Further, the fuel cell system according to the invention described in claim 6 is, for example, as shown in FIG. 1, in the fuel cell system 10 according to claim 5 , the calculation unit 41 includes a power generation current of the fuel cell 30, Stationary fuel cell inlet air, which is the pressure of the power generation air t introduced into the fuel cell 30 when the power generation air t at a flow rate for generating the power generation current is introduced into the fuel cell 30 at the second predetermined oxygen utilization rate. The relationship between the pressure and the pressure is stored in advance; the calculation unit 41 further supplies the fuel cell 30 with the fuel cell resistance coefficient that fluctuates following the fluctuation of the generated current of the fuel cell 30 and the steady fuel cell inlet air pressure. It is configured to calculate a target fuel cell inlet air pressure, which is a target pressure of the introduced power generation air t; the control device 40 detects the pressure detected by the pressure detector 44 as the target fuel cell inlet air. Is configured to control the air supply means 42 so that the force Pt.

  If comprised in this way, even if the pressure loss of a fuel cell fluctuates, the air for electric power generation of an appropriate flow rate can be supplied to a fuel cell.

  According to the present invention, the air supply means for supplying the combustion air to the combustion section and the power generation air to the fuel cell is provided, so that the air is supplied to the combustion section of the fuel cell and the fuel processing device by one air supply means. Can be supplied. In addition, since the combustion air flow rate adjusting means is controlled so that the ratio of the flow rate of oxygen in the combustion air to the flow rate of combustible components in the fuel in the combustion section becomes a predetermined ratio, it is particularly suitable for the combustion section. A flow rate of combustion air can be supplied, and emission of carbon monoxide accompanying incomplete combustion of fuel can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, a fuel cell system 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of the fuel cell system 10. The fuel cell system 10 includes, as main components, a fuel processing device 20 that generates a reformed gas g rich in hydrogen, a fuel cell 30 that generates electricity by an electrochemical reaction between hydrogen and oxygen, a fuel processing device 20, An air blower 42 as air supply means for supplying air to the fuel cell 30 and a control device 40 for controlling the operation of the fuel cell system 10 are provided.

  The fuel processor 20 introduces the raw material m1 and the process water s and generates a reformed gas g rich in hydrogen by a steam reforming reaction, and the reforming heat used for the steam reforming reaction of the raw material m1. And a combustion section 23 that is generated. The raw material m1 is typically a chain hydrocarbon (including natural gas) such as methane or ethane, or a mixture mainly composed of hydrocarbons such as methanol and petroleum products (kerosene, gasoline, naphtha, LPG, etc.) A hydrocarbon-based fuel such as that suitable for combustion for heating is used. The process water s introduced into the reforming unit 25 may be steam. The reformed gas g rich in hydrogen is a gas containing hydrogen as a main component, and is a gas supplied to the fuel cell 30 containing hydrogen in an amount of 40% by volume or more, typically about 70 to 80% by volume. is there. The hydrogen concentration in the reformed gas g may be 80% by volume or more, that is, any concentration that allows power generation by an electrochemical reaction with oxygen in the power generation air t when supplied to the fuel cell 30.

  The reforming unit 25 is filled with a reforming catalyst and configured to promote a steam reforming reaction. As the reforming catalyst, a nickel-based reforming catalyst or a ruthenium-based reforming catalyst is typically used. If the gas rich in hydrogen produced by reforming the raw material m1 by the action of the reforming catalyst contains a predetermined amount or more of carbon monoxide, the electrode catalyst of the fuel cell 30 is poisoned. Therefore, the reforming unit 25 has a shift unit (not shown) filled with a shift catalyst and a selective oxidation unit (not shown) filled with a selective oxidation catalyst, and is reformed derived from the fuel processor 20. It is preferable that the concentration of carbon monoxide in the gas g is about 10 ppm by volume or less, preferably about 1 ppm by volume. As the shift catalyst, typically, an iron-chromium shift catalyst, a copper-zinc shift catalyst, a platinum shift catalyst, or the like is used. Typically, a platinum-based selective oxidation catalyst, a ruthenium-based selective oxidation catalyst, a platinum-ruthenium-based selective oxidation catalyst, or the like is used as the selective oxidation catalyst. The reaction in the reforming catalyst is an endothermic reaction, but the reaction in the shift part having the shift catalyst and the selective oxidation part having the selective oxidation catalyst is an exothermic reaction.

  A raw material pipe 56A for introducing the raw material m1 and a process water pipe 59 for introducing the process water s are connected to the reforming unit 25. If the process water pipe 59 is connected to the raw material pipe 56A closest to the reforming section 25, it is preferable that the process water pipe 59 is introduced into the reforming section 25 in a state where the raw material m1 and the process water s are mixed. However, the process water pipe 59 may be directly connected to the reforming unit 25. A raw material adjusting valve 66A is provided in the raw material pipe 56A. The raw material adjustment valve 66A is connected to the control device 40 through a signal cable, and is configured to receive a signal from the control device 40 and adjust the opening of the valve. The raw material pipe 56A is provided with a raw material flow meter 46 for detecting the flow rate of the raw material m1 introduced into the reforming unit 25. The raw material flow meter 46 is connected to the control device 40 with a signal cable, and is configured to be able to transmit the measured flow rate of the raw material m1 to the control device 40 as a signal. In addition, a reformed gas pipe 51 for deriving the reformed gas g is connected to the reforming unit 25 (in the case where the reformed gas has a site for reducing the carbon monoxide concentration).

  The combustion unit 23 is disposed in the fuel processing apparatus 20 so as to be adjacent to a position where the reforming catalyst of the reforming unit 25 is provided. The combustion unit 23 introduces a combustion fuel m2 that is a hydrocarbon-based fuel, an anode off-gas p and a reformed gas g that are hydrogen-containing gas, and is a part for air that is sent by an air blower 42 Air a is introduced, and these are burned by a burner (not shown) so as to obtain reforming heat used for the steam reforming reaction. Depending on the state of the fuel cell system 10, the combustion unit 23 introduces one or more of the combustion fuel m2, the anode offgas p, and the reformed gas g and burns them. In the present embodiment, the same combustion fuel m2 as the raw material m1 is used. That is, the raw material m1 and the combustion fuel m2 are obtained by changing the names of the raw material fuel m flowing through the raw material fuel pipe 56 depending on the application, and the components are the same. The raw fuel pipe 56 is provided with a fuel blower (not shown) for sending gaseous raw fuel m. When the raw material fuel m is liquid, a fuel pump (not shown) is provided instead of a fuel blower (not shown). The combustion unit 23 is provided with a burner (not shown) as a device for generating reforming heat. An anode offgas pipe 52 capable of introducing the anode offgas p and the reformed gas g and a fuel pipe 56B for introducing the combustion fuel m2 are connected to the combustion unit 23. A combustion air pipe 58 as a combustion air supply line for introducing the combustion air a is connected to the fuel pipe 56B. A combustion control valve 66B and a check valve 66C are arranged in this order from upstream to downstream in the fuel pipe 56B upstream of the position where the combustion air pipe 58 is connected. The combustion control valve 66B is connected to the control device 40 via a signal cable, and is configured to receive a signal from the control device 40 and adjust the opening of the valve.

  The combustion air pipe 58 is provided with a combustion air flow meter 48 as combustion air flow rate detection means for measuring the flow rate of the combustion air a. The combustion air flow meter 48 uses a mass flow sensor that detects a mass flow rate such as a thermal flow meter, and can detect the flow rate of the combustion air a in a standard state without requiring correction of temperature and pressure. it can. The combustion air flow meter 48 is connected to the control device 40 through a signal cable, and is configured to transmit the measured flow rate of the combustion air a as a signal to the control device 40.

  Further, the combustion air pipe 58 has a first combustion air pipe 58A and a second combustion air pipe so that the flow path of the combustion air a is partially divided into two on the upstream side of the combustion air flow meter 48. Two pipes 58B are arranged in parallel. That is, one combustion air pipe 58 is divided into two, a first combustion air pipe 58A and a second combustion air pipe 58B, and merges again to form one combustion air pipe 58. It is configured. The first combustion air pipe 58A is provided with an orifice 68A as a throttle means. The second combustion air pipe 58B is provided with an orifice 68B as a throttle means. The orifice 68B has a pressure loss different from that of the orifice 68A. In the present embodiment, the orifice 68B has a larger pressure loss than the orifice 68A. The plurality of orifices 68A and 68B having different pressure losses constitute a throttle means group 68GP. A throttle selection three-way valve 68 is disposed at a branch portion where the combustion air pipe 58 is divided into a first combustion air pipe 58A and a second combustion air pipe 58B. By switching the throttle selection three-way valve 68, the flow path of the combustion air a can be switched to the first combustion air pipe 58A or the second combustion air pipe 58B. The throttle selection three-way valve 68 is connected to the control device 40 through a signal cable, and is configured to receive a signal from the control device 40 and perform a valve switching operation. In the present embodiment, by using the orifices 68A and 68B as the throttle means, the cost of the system is reduced as compared with the case where the control valve is used.

The fuel cell 30 is typically a polymer electrolyte fuel cell. The fuel cell 30 generates heat generated by an electrochemical reaction, an anode 31 that introduces the reformed gas g, a cathode 32 that introduces power generation air t that is part of the air sent by the air blower 42, and the like. It includes a cooling unit (not shown) to be taken. The power generation air t introduced into the cathode 32 functions as an oxidant gas. Although the fuel cell 30 is shown in a simplified manner in the drawing, in practice, a single cell is formed by sandwiching a solid polymer membrane between an anode 31 and a cathode 32, and a plurality of cells are connected via a cooling unit. It is configured by stacking sheets. In the fuel cell 30, hydrogen in the reformed gas g supplied to the anode 31 is decomposed into hydrogen ions and electrons, and the hydrogen ions pass through the solid polymer film and move to the cathode 32, and the electrons move to the anode 31. It moves to the cathode 32 through a conducting wire connecting to the cathode 32, reacts with oxygen in the power generation air t supplied to the cathode 32 to generate water, and generates heat during this reaction. When this reaction is represented by a chemical formula, the anode 31 side is represented by the following formula (1), and the cathode 32 side is represented by the following formula (2).
_{^{2H 2 → 4H + + 4e -}} ··· (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
In this reaction, the direct current can be taken out by passing electrons through the conducting wire. The fuel cell 30 is connected with an ammeter 43 as a generated current detection means for detecting the generated current. The ammeter 43 is typically disposed on a cable (not shown) that transmits the current generated by the fuel cell 30. The fuel cell 30 is typically electrically connected to a power conditioner (not shown) that converts DC power into AC power.

  In the anode 31 of the fuel cell 30, not all of the hydrogen in the introduced reformed gas g is used for the above-described electrochemical reaction (power generation in the fuel cell 30), but some hydrogen is used. . The percentage of the ratio of the hydrogen used for power generation to the hydrogen introduced into the anode 31 is referred to as the hydrogen utilization rate and is represented by the symbol Ry (“Ry = (hydrogen used for power generation / introduced to the fuel cell 30)”. Hydrogen) × 100 (%) ”). From the anode 31, the anode off gas p containing hydrogen that has not been used for the electrochemical reaction in the fuel cell 30 is discharged. The components of the anode off gas p typically include about half of hydrogen and the other half of carbon dioxide, nitrogen, and methane.

  In the cathode 32 of the fuel cell 30, not all of the oxygen in the introduced power generation air t is used for the above-described electrochemical reaction (power generation in the fuel cell 30), but some oxygen is used. . The percentage of the ratio of oxygen used for power generation to oxygen introduced to the cathode 32 is referred to as oxygen utilization, and is represented by the symbol Rx (“Rx = (Oxygen used for power generation / introduced to fuel cell 30). Oxygen) x 100 (%) "). From the cathode 32, a cathode offgas q containing oxygen that has not been used for the electrochemical reaction in the fuel cell 30 is discharged.

  The anode 31 and the reforming unit 25 are connected via a reformed gas pipe 51. Further, the anode 31 and the combustion part 23 are connected via an anode offgas pipe 52 so that the anode offgas p can be introduced into the combustion part 23. An anode off gas valve 62 is disposed in the anode off gas pipe 52. An anode offgas pipe 52 and the reformed gas pipe 51 downstream of the anode offgas valve 62 are connected by a bypass pipe 53. A reformed gas three-way valve 61 is provided at a branch portion where the bypass pipe 53 branches from the reformed gas pipe 51. Instead of providing the reformed gas three-way valve 61, a two-way valve is provided in the reformed gas pipe 51 on the downstream side of the branch portion where the bypass pipe 53 branches, and a two-way valve is provided in the bypass pipe 53. The flow path of the reformed gas g may be switched by opening and closing the valve.

  A power generation air pipe 54 as a power generation air supply line for introducing power generation air t and a cathode offgas pipe 55 for discharging the cathode offgas q are connected to the cathode 32. The power generation air pipe 54 is one of the pipes branched from the mixed air pipe 57, and the other one branched from the mixed air pipe 57 is the combustion air pipe 58. A power generation air shut-off valve 64 is provided in the power generation air pipe 54. The power generation air shut-off valve 64 is connected to the control device 40 via a signal cable, and is configured to receive a signal from the control device 40 and to open and close the valve. A pressure sensor 44 is disposed in the power generation air pipe 54. The pressure sensor 44 is connected to the control device 40 through a signal cable, and is configured to transmit the detected pressure in the power generation air pipe 54 to the control device 40 as a signal. Further, a humidifying device (not shown) for humidifying the power generation air t to a predetermined humidity in order to maintain the conductivity of the solid polymer film (see paragraph 0028) of the fuel cell 30 is provided in the power generation air pipe 54. ) Is disposed.

  The air blower 42 is disposed in the mixed air pipe 57. Typically, the air blower 42 is configured to rotate the impeller attached to the shaft of the motor and discharge the sucked air by rotating the motor. The motor of the air blower 42 is configured to obtain power through an inverter 42v as a rotation speed adjusting means, and the rotation speed of the motor can be adjusted by adjusting the electric power input by the inverter 42v. It is configured. By making the rotational speed of the motor adjustable, the rotational speed of the impeller can be adjusted in conjunction with it, and the flow rate of air discharged from the air blower 42 can be adjusted.

  The control device 40 can transmit signals to the reformed gas three-way valve 61, the anode off-gas valve 62, the power generation air shut-off valve 64, and the throttle selection three-way valve 68, respectively, to switch or open / close each valve. Further, the control device 40 can transmit signals to the raw material control valve 66A and the combustion control valve 66B, respectively, and adjust the opening degree of each valve. In addition, the control device 40 transmits a signal to the inverter 42v, and controls the operation and stop of the air blower 42 and the rotational speed of the motor. In addition, the control device 40 receives signals from the ammeter 43, the pressure sensor 44, the raw material flow meter 46, and the combustion air flow meter 48, performs various calculations in the calculation unit 41 described later, and takes each detected situation. Based on this, the fuel cell system 10 is controlled.

In addition, the control device 40 includes a calculation unit 41. The calculation unit 41 stores the relationship between the pressure and flow rate of the power generation air t introduced into the fuel cell 30. The relationship between the pressure and the flow rate of the power generation air t introduced into the fuel cell 30 is inherent to the fuel cell 30 with a fixed resistance system, the power generation air pipe 54 and the cathode offgas pipe 55. It is required by trial operation.
FIG. 2 shows a graph of the relationship between the pressure and flow rate of power generation air t introduced into the fuel cell 30. In the graph of FIG. 2, the vertical axis represents the pressure P, the horizontal axis represents the flow rate Q, and the curve F represents the relationship between the pressure P of the power generation air t introduced into the fuel cell 30 and the flow rate Q. The curve F is typically a quadratic curve that rises to the right. Although described with reference to FIG. 2 for convenience, the calculation unit 41 may store the curve F as a function.

Further, the calculation unit 41 stores the relationship between the flow rate of the power generation air t introduced into the fuel cell 30 and the output of the fuel cell 30 for each oxygen utilization rate Rx in the fuel cell 30.
FIG. 3 is a graph showing the relationship between the flow rate of power generation air t introduced into the fuel cell 30 and the output of the fuel cell 30 using the oxygen utilization rate Rx as a parameter. In the graph of FIG. 3, the vertical axis indicates the flow rate Q of the power generation air t introduced into the fuel cell 30, and the horizontal axis indicates the output G of the fuel cell 30 as a percentage of the rated output. In the present embodiment, the graph is a straight line rising to the right. In the present embodiment, the minimum output of the fuel cell 30 is 30% of the rated output, so that the fuel cell 30 does not operate at an output less than the minimum output.

Further, the calculation unit 41 stores a relationship between the generated current I in the fuel cell 30 and the moisture amount Ws in the steady assumed stack. Here, the moisture amount Ws in the normal assumed stack is the amount of moisture theoretically generated for a certain generated current generated by the fuel cell 30 and the fuel cell attached to the power generation air t to generate the current. This is the amount of water that is assumed to exist in the fuel cell 30 from the amount of water that is brought into the fuel cell 30, and is the amount of water when the operation history of the fuel cell 30 is not taken into account when the amount of water is assumed.
FIG. 4 collectively shows the relationship between the generated current I in the fuel cell 30 and the moisture amount Ws in the steady assumed stack. The moisture amount Ws in the steady assumed stack increases and decreases following the increase and decrease of the generated current I of the fuel cell 30.

  In addition, the calculation unit 41 stores a power generation initial assumed stack water amount Wp that is a water amount assumed to exist in the fuel cell 30 in the early stage of power generation of the fuel cell 30. The initial stage of power generation is the time until the temperature of the fuel cell 30 reaches the temperature during steady operation (about 60 to 80 ° C.). The amount of water in the fuel cell 30 assumed in the initial stage of power generation is the fuel cell 30. Is lower than that in the steady operation, and thus the moisture amount Ws in the steady stack for the generated current I during the steady operation is larger. The power generation initial assumed water content Wp in the stack is a value unique to the fuel cell 30 and is 70 in the present embodiment.

  Further, in the calculation unit 41, a combustible component in the anode offgas p introduced into the combustion unit 23 from the flow rate of the raw material m 1 detected by the raw material flow meter 46 and the generated current of the fuel cell 30 detected by the ammeter 43. It is comprised so that the flow volume of can be calculated. The process of calculating the flow rate of the combustible component in the anode off gas p will be described in detail as follows. First, the flow rate of the raw material m1 introduced into the fuel processor 20 is detected by the raw material flow meter 46. The calculation unit 41 stores the flow rate of the reformed gas g generated with respect to the introduced raw material m1 during steady operation and the ratio of combustible components such as hydrogen and methane in the reformed gas g per unit flow rate. Based on this, the flow rate of the combustible component in the reformed gas g is calculated. Next, the flow rate of hydrogen consumed in the fuel cell 30 is calculated from the generated current detected by the ammeter 43 based on the above equation (1). The difference between the flow rate of the combustible component in the reformed gas g produced by the fuel processor 20 and the flow rate of hydrogen consumed in the fuel cell 30 is the flow rate of the combustible component in the anode offgas p introduced into the combustion unit 23. Become.

  In the fuel cell system 10, the raw material flow meter 46, the ammeter 43, and the calculation unit 41 constitute fuel flow grasping means. Further, the pressure sensor 44 and the calculation unit 41 constitute power generation air detection means. The air blower 42, the throttle means group 68GP, and the throttle selection three-way valve 68 constitute combustion air flow rate adjusting means.

  With continued reference to FIG. 1, the operation of the fuel cell system 10 will be described. In order to start the operation of the stopped fuel cell system 10, the combustion fuel m <b> 2 is supplied to the combustion unit 23 and the air blower 42 is activated to supply the combustion air a to the combustion unit 23. At this time, the power generation air shutoff valve 64 is closed so that the power generation air t is not supplied to the fuel cell 30. As a result, the solid polymer membrane of the fuel cell 30 is prevented from being dried and the catalyst is prevented from being oxidized, thereby preventing the performance of the fuel cell 30 from being lowered. Further, the throttle selection three-way valve 68 is open on the first combustion air pipe 58A side where the orifice 68A having the smaller pressure loss is disposed, and closed on the second combustion air pipe 58B side. The combustion control valve 66B is open, and the raw material control valve 66A and the anode off-gas valve 62 are closed. The reformed gas three-way valve 61 is open on the bypass pipe 53 side.

  When the combustion fuel m2 is combusted in the combustion section 23 to generate reforming heat and the temperature of the reforming section 25 rises, the raw material control valve 66A is opened to introduce the raw material m1 into the reforming section 25. The temperature of the reforming unit 25 is detected by a temperature detector (not shown). Process water s is also introduced into the reforming section 25, and the reforming heat is obtained from the combustion section 23, the raw material m1 undergoes a steam reforming reaction, and reformed gas g is generated. In the fuel processing device 20, the reformed gas g is generated as described above, but since the composition of the reformed gas g is not stable at the beginning of operation, the bypass pipe 53 side of the reformed gas three-way valve 61 is opened. Thus, the reformed gas g having an unstable composition is led to the combustion section 23 without being supplied to the fuel cell 30 and burned. At this time, the reformed gas g having an unstable composition introduced into the combustion unit 23 is mainly combusted, and the insufficient amount of combustion fuel m2 is introduced into the combustion unit 23 by adjusting the opening of the combustion control valve 66B. When the reformed gas g whose composition is not stable is sufficient, the combustion control valve 66B is closed.

  When the composition of the reformed gas g generated in the fuel processing device 20 becomes stable, the control device 40 opens the anode offgas valve 62 and closes the bypass pipe 53 side of the reformed gas three-way valve 61 to improve the reformed gas g. The quality gas g is introduced into the fuel cell 30. As a result, the reformed gas g is introduced into the anode 31 of the fuel cell 30. On the other hand, the control device 40 opens the power generation air shut-off valve 64, whereby the power generation air t is introduced to the cathode 32 of the fuel cell 30. At this time, the control device 40 increases the rotational speed of the air blower 42 so that air that has been increased by the amount supplied to the fuel cell 30 is discharged from the air blower 42. In the fuel cell 30, as shown in the above formulas (1) and (2) by hydrogen in the reformed gas g introduced into the anode 31 and oxygen in the power generation air t introduced into the cathode 32. An electrochemical reaction takes place. Electricity is generated by this electrochemical reaction, heat is generated, and moisture is generated. In further explanation, electric power can be obtained when electrons on the anode 31 side move to the cathode 32 side through the external electric circuit. Hydrogen ions on the anode 31 side pass through the solid polymer membrane and move to the cathode 32 side, and combine with oxygen to generate moisture (see the above formula (2)). This electrochemical reaction is an exothermic reaction.

  Since the power obtained by the fuel cell 30 is DC power, it is converted into AC power by a power conditioner (not shown) and transmitted to a power load (not shown). Further, the heat generated in the fuel cell 30 is stored, for example, in a hot water storage tank (not shown), and is consumed in a heat load such as hot water supply or heating as necessary. By effectively using the heat generated in the fuel cell 30, the efficiency of the fuel cell system 10 is improved.

  During the operation of the fuel cell 30, the anode off gas p is discharged from the anode 31. The discharged anode off gas p is guided to the combustion unit 23 of the fuel processing apparatus 20 through the anode off gas pipe 52 and burned. By the combustion of the anode off gas p in the combustion unit 23, reforming heat used for reforming in the reforming unit 25 can be generated. Exhaust gas generated by combustion in the combustion unit 23 is discharged out of the system through an exhaust gas pipe (not shown). On the other hand, the cathode offgas q is discharged from the cathode 32 and discharged outside the system via the cathode offgas pipe 55.

  During the operation of the fuel cell system 10 as described above, the ratio of the amount Mo of oxygen in the combustion air a introduced into the combustion section 23 to the amount Mp of combustible components in the fuel p (hereinafter referred to as “oxygen combustible component ratio Rm”). "(Rm = Mo / Mp)" is set to a predetermined ratio, the control device 40 controls the air blower 42 and the throttle selection three-way valve 68. Since the proportion of oxygen in the combustion air a is substantially constant regardless of the passage of time, the flow rate of oxygen in the combustion air a can be adjusted by adjusting the flow rate of the combustion air a. That is, even when the flow rate of the combustion air a is directly adjusted by the flow meter 48, the flow rate of oxygen in the combustion air a is substantially adjusted. By setting the oxygen combustible component ratio Rm to a predetermined ratio, it is possible to prevent misfire due to excessive combustion air a, and to prevent discharge of harmful substances due to incomplete combustion of the fuel p due to insufficient combustion air a. Can do. The predetermined ratio is such that combustion in the combustion section 23 does not become incomplete combustion, and is about 1.15 to 1.50 in the present embodiment.

  Further, during the operation of the fuel cell system 10 as described above, the control device 40 controls the air blower 42 so that the oxygen utilization rate Rx in the fuel cell 30 becomes the first predetermined utilization rate. The oxygen used for power generation is obtained from the generated current detected by the ammeter 43 and the above equation (2). The flow rate of oxygen introduced into the fuel cell 30 is calculated by the calculation unit 41 based on the pressure detected by the pressure sensor 44. When the oxygen utilization rate Rx exceeds the upper limit, the distribution of oxygen to each cell (see paragraph 0028) constituting the fuel cell 30 is not uniform, resulting in a shortage of oxygen, resulting in a voltage drop in the fuel cell 30. Will be invited. On the other hand, when the oxygen utilization rate Rx falls below the lower limit, the load of the air blower 42 increases, and the power generation efficiency of the fuel cell system 10 (ratio of generated electric energy to input energy; the same applies hereinafter) decreases and humidification occurs. When the capacity of the device (see paragraph 0032) is insufficient, the operation becomes low humidification, and the power generation voltage of the fuel cell 30 is lowered to affect the durability of the fuel cell 30. In order to avoid these problems, the oxygen utilization rate Rx is maintained at the first predetermined utilization rate. The first predetermined utilization rate is set to a value that does not cause the above-described problem, and is set to 45 to 59% in the present embodiment, but is appropriately optimized depending on the characteristics of the fuel cell 30 to be used. A value should be set. Thus, the first predetermined utilization rate typically has a width.

  Further, during the operation of the fuel cell system 10 as described above, the control device 40 controls the fuel processing device 20 so that the utilization rate of hydrogen in the fuel cell 30 becomes the third predetermined utilization rate. Hydrogen used for power generation is obtained from the power generation current detected by the ammeter 43 and the above-described equation (2). The flow rate of hydrogen introduced into the fuel cell 30 is obtained as a unique value of the fuel processor 20 based on the type and flow rate of the raw material m1 introduced into the reforming unit 25 detected by the raw material flow meter 46. If the hydrogen utilization rate Ry exceeds the upper limit, the distribution of hydrogen to each cell (see paragraph 0028) constituting the fuel cell 30 is not uniform, resulting in cells that are deficient in hydrogen and the voltage of the fuel cell 30 is reduced. Invite you and cause cell degradation. On the other hand, when the hydrogen utilization rate Ry falls below the lower limit, the load of the fuel processing device 20 increases, and the power generation efficiency of the fuel cell system 10 decreases. In order to avoid these problems, the hydrogen utilization rate Ry is maintained at the third predetermined utilization rate. The third predetermined utilization rate is set to a value that does not cause the above-described problems, and in the present embodiment, is set to be as close to 75% as possible within the range of 70 to 80%. An optimal value may be set as appropriate according to the 30 characteristics.

  The magnitude of the generated current in the fuel cell 30 is arbitrarily set between the minimum power generation amount (30% of the rated output in the present embodiment, see paragraph 0036) and the rated output, depending on the setting of the power conditioner (see paragraph 0028). Can be determined. The amount of hydrogen and oxygen used for power generation in the fuel cell 30 are determined by the determined magnitude of the current. The hydrogen utilization rate Ry and oxygen utilization rate Rx in the fuel cell 30 are determined depending on how much the reformed gas g and the power generation air t are supplied with respect to the determined amount of hydrogen and oxygen. The hydrogen utilization rate Ry and the oxygen utilization rate Rx are independent, and there is no correlation between the two.

  In order to set the hydrogen utilization rate Ry to the third predetermined utilization rate, the flow rate of the raw material m1 introduced into the reforming unit 25 is adjusted by the raw material control valve 66A. As a result, the flow rate of the reformed gas g produced by the fuel processor 20 can be adjusted, the flow rate of the reformed gas g supplied to the anode 31 of the fuel cell 30 can be adjusted, and the fuel cell. The hydrogen utilization rate Ry at 30 can be maintained at the third predetermined utilization rate.

  On the other hand, in order to set the oxygen utilization rate Rx to the first predetermined utilization rate, the rotational speed of the air blower 42 is adjusted. In the fuel cell system 10, power generation air t is generated by one air blower 42. Is supplied to the fuel cell 30 and the combustion air a is supplied to the combustion unit 23, so that the oxygen combustible component ratio Rm in the combustion unit 23 becomes a predetermined ratio and oxygen is used in the fuel cell 30. The control device 40 adjusts the rotational speed of the air blower 42 so that the rate Rx becomes the first predetermined utilization rate. The supply amount of combustion air a to the combustion unit 23 is monitored by a flow meter 48, and the supply amount of power generation air t to the fuel cell 30 is monitored by a pressure sensor 44. At this time, the pressure value detected by the pressure sensor 44 may be set to the steady fuel cell inlet air pressure Ps. Here, the steady fuel cell inlet air pressure Ps is the fuel cell when the power generation air t is introduced into the fuel cell 30 at a flow rate that provides the second predetermined oxygen utilization rate in order to obtain a set power generation current. Inlet air pressure. The utilization rate of the second predetermined oxygen is a design (preferred) utilization rate of oxygen set within the first predetermined utilization rate, and is 50% in the present embodiment. When the air blower 42 is controlled with the steady fuel cell inlet air pressure Ps as a target, a flow rate that becomes the steady fuel cell inlet air pressure Ps is supplied to the fuel cell 30 in balance with the combustion air a supplied to the combustion unit 23. Even if this is not possible, the probability that the oxygen utilization rate Rx in the fuel cell 30 falls within the range of the first predetermined utilization rate increases.

  When the rotation rate of the air blower 42 is adjusted so that the oxygen combustible component ratio Rm in the combustion unit 23 becomes a predetermined ratio, the control device is used when the oxygen utilization rate Rx in the fuel cell 30 does not become the first predetermined utilization rate. 40 transmits a signal to the throttle selection three-way valve 68 to switch the opening direction of the valve to switch the orifice 68A through which the combustion air a should flow to the orifice 68B. When the oxygen utilization rate Rx in the fuel cell 30 is higher than the first predetermined utilization rate (the flow rate of the power generation air t supplied to the fuel cell 30 is small), the pressure is switched to the orifice 68B where the pressure loss increases. The flow rate of the power generation air t flowing toward the air pipe 54 is increased. On the contrary, when the oxygen utilization rate Rx in the fuel cell 30 is lower than the first predetermined utilization rate (the flow rate of the power generation air t supplied to the fuel cell 30 is large), the pressure is switched to the orifice 68A. Thus, the flow rate of the power generation air t flowing toward the power generation air pipe 54 is reduced. That is, when the orifice 68B is used, the flow rate of the combustion air a flowing through the combustion air pipe 58 increases in the order in which the orifice 68A is used. By switching the orifices 68A and 68B in this way, the pressure loss on the combustion air a side can be controlled and supplied to the fuel cell 30 when the oxygen combustible component ratio Rm is controlled to be a predetermined ratio. The flow rate of the generated power generation air t can be optimized (so that the oxygen utilization rate Rx becomes the first predetermined utilization rate).

  By the way, as is clear from the above-described equation (2), water is generated in the fuel cell 30 as the fuel cell 30 generates power. Further, the water generated in the fuel cell 30 includes humidified water that is carried by the power generation air t in addition to the one accompanying the electrochemical reaction shown in the equation (2). Although it can be understood from the above-described equation (2) that the amount of water generated in the fuel cell 30 is substantially proportional to the generated current of the fuel cell 30, the present inventor We tried to follow the change in the generated current, but the change was slow and we found that there was a difference from the theoretical value. The moisture in the fuel cell 30 causes a pressure loss of the power generation air t supplied to the fuel cell 30, changes the flow rate of the power generation air t supplied to the fuel cell 30, and in turn uses oxygen in the fuel cell 30. The rate Rx is changed. That is, due to the presence of moisture generated by power generation, air at an appropriate flow rate is supplied to the combustion unit 23 and the fuel cell 30 only by changing the rotation speed of the air blower 42 according to the power generation current of the fuel cell 30. Difficult to do. Therefore, it is preferable to correct the steady fuel cell inlet air pressure Ps, which is the control target of the rotational speed of the air blower 42, according to the amount of water in the fuel cell 30.

  The present inventor, after earnest research, calculates a pressure detected by the pressure sensor 44 as a control target of the rotational speed of the air blower 42 by multiplying the steady fuel cell inlet air pressure Ps by the fuel cell resistance coefficient φ. It was found that the flow rate of the power generation air t supplied to the fuel cell 30 can be optimized by correcting the fuel cell inlet air pressure Pt (Pt = Ps × φ). The fuel cell resistance coefficient φ is a coefficient indicating the degree of fluctuation of the pressure loss of the cathode 32 due to fluctuation of the power generation current of the fuel cell 30, and is assumed to be present in the fuel cell 30 at a certain point in the present embodiment. The water amount Wt in the currently assumed stack, which is the amount of water to be obtained, is divided by the water amount Ws in the steady assumed stack (see paragraph 0037) described above (φ = Wt / Ws). Here, the currently assumed moisture content Wt in the stack takes into account the operation history of the fuel cell 30 in assuming the moisture content. In addition to the amount of water in the fuel cell 30, the fuel cell resistance coefficient φ may be defined by the temperature of the fuel cell 30 and other conditions, but the fuel cell system 10 according to the present embodiment In controlling, it is possible to supply air at an appropriate flow rate to the fuel cell 30 and the combustion unit 23 of the fuel processing device 20 even if it is considered to have a correlation with the amount of water present in the fuel cell 30. It has become. Note that the currently assumed moisture content Wt in the stack is obtained as follows.

As described above, the moisture present in the fuel cell 30 changes every moment by following the change in the generated current and the change following the change. Therefore, the control device 40 obtains the currently assumed moisture content Wt in the stack for each predetermined time step and reflects it in the fuel cell resistance coefficient φ. The currently assumed stack moisture amount Wt is calculated from the difference between the steady assumed stack moisture amount Ws and the currently assumed stack moisture amount Wt ′ one time step before, where the coefficient is f and the time step is dt. (3).
Wt = f × (Ws−Wt ′) × dt + Wt ′ (3)
For example, assuming that the coefficient f = 0.15 and the time step dt is 1 second, the currently assumed moisture content Wt in the stack is expressed by the following equation (4).
Wt = 0.15 × (Ws−Wt ′) × 1 + Wt ′ (4)
As described above, by correcting the steady fuel cell inlet air pressure Ps, which is the control target of the rotational speed of the air blower 42, to the target fuel cell inlet air pressure Pt, the pressure of the fuel cell 30 is determined according to the operation history of the fuel cell system 10. Even if the loss fluctuates, it is possible to supply the air (combustion air a and power generation air t) at an optimal flow rate to the combustion unit 23 and the fuel cell 30 with a single air blower 42.

  FIG. 5 shows how the target fuel cell inlet air pressure Pt fluctuates as the power generation current of the fuel cell 30 fluctuates. In the figure, the curve I represents the generated current I in the fuel cell 30, the curve Ws represents the steady assumed stack moisture amount Ws, the curve Wt represents the currently assumed stack moisture amount Wt, and the curve Ps represents the steady fuel cell inlet air pressure Ps. Curve Pt represents the target fuel cell inlet air pressure Pt. From the figure, the currently assumed stack moisture amount Wt follows the steady assumed stack moisture amount Ws with a delay, and the target fuel cell inlet air pressure Pt reflects the fluctuation of the currently assumed stack moisture amount Wt. I understand.

  As described above, according to the fuel cell system 10 according to the embodiment of the present invention, air (combustion air a and power generation) with a suitable flow rate for the combustion unit 23 and the fuel cell 30 with one air blower 42. The working air t) can be supplied. The cost of the fuel cell system 10 is reduced by using one air blower for supplying air to the combustion unit 23 and the fuel cell 30. The cost is also reduced by using a pressure gauge 44 as a gauge for monitoring the flow rate of the power generation air t supplied to the fuel cell 30.

  In the above description of the preferred embodiment of the present invention, the rotational speed of the air blower 42 is corrected according to the amount of water present in the fuel cell 30, but a slight decrease in power generation efficiency is overlooked (fuel cell). It is possible to simplify the control by appropriately adjusting the flow rate of the combustion air a supplied to the combustion unit 23 (with the approval that the oxygen utilization rate Rx at 30 is outside the first predetermined utilization rate). it can.

  In the above description, two combustion air pipes constituting the throttle means group are arranged in parallel. However, three or more combustion air pipes may be arranged in parallel. At this time, throttle means having different pressure losses are arranged in the combustion air pipes arranged in parallel. Moreover, although the throttle means has been described as an orifice, it may be a filter, a two-way valve, or the like. When an automatic two-way valve is provided as the throttle means, the throttle selection three-way valve can be omitted, and the pressure loss of one combustion air pipe can be made variable. When the orifice is used, the cost can be reduced as compared with the case where the automatic two-way valve is used. Further, the combustion air a passing through the throttle means group is supplied not only through one combustion air pipe but also downstream of the throttle means group by passing through two or more combustion air pipes. The flow rate of the combustion air a may be adjusted.

  In the above description, the combustion air flow meter 48 is a mass flow sensor that detects a mass flow rate such as a thermal flow meter, but other differential pressure flow meters, vortex flow meters, and the like may be used. The differential pressure flow meter has a simple structure and is inexpensive, and the vortex flow meter has an advantage that there is no moving part and the structure is simple and maintenance is not required. However, the mass flow sensor is preferable because the mass flow rate of the gas can be directly measured without correcting the temperature and pressure.

  In the above description, the control device 40 makes the ratio of the flow rate of the combustion air a in the combustion section 23 to the flow rate of the fuel p a predetermined air ratio, and the oxygen utilization rate in the fuel cell 30 is the first predetermined rate. The inverter 42v and the throttling selection three-way valve 68 are controlled so that the utilization rate of the fuel cell 30 becomes equal, but when the flow rate of the power generation air t supplied to the fuel cell 30 is allowed to become a desired flow rate (fuel cell) (When it is approved that the oxygen utilization rate Rx at 30 deviates from the first predetermined utilization rate), the oxygen utilization rate at the fuel cell 30 is excluded from the object of control, and the combustion air a in the combustion section 23 The combustion air flow rate adjusting means 42 and 68GP may be controlled so that the ratio of the flow rate to the flow rate of the fuel p becomes a predetermined air ratio. In this way, while supplying air to the fuel cell 30 and the combustion unit 23 of the fuel processing apparatus 20 with one air supply means 42, the emission of carbon monoxide accompanying incomplete combustion of fuel in the combustion unit 23 is reduced. And the control can be simplified.

  In the above description, the fuel cell 30 has been described as a polymer electrolyte fuel cell, but may be a fuel cell other than a polymer electrolyte fuel cell such as a phosphoric acid fuel cell. However, the polymer electrolyte fuel cell can be operated at a relatively low temperature and can be downsized, so that it is suitable for installation in a general household.

1 is a schematic system diagram of a fuel cell system according to an embodiment of the present invention. It is a graph which shows the relationship between the pressure and flow volume of the air for electric power generation introduced into a fuel cell. It is a graph which shows the relationship between the flow volume of the air for electric power introduced into the fuel cell which made oxygen utilization factor the parameter, and the output of a fuel cell. It is a figure of the table of the relationship between the electric power generation electric current in a fuel cell, and the moisture content in a steady assumption stack | stack. It is a graph which shows the mode of the fluctuation | variation of the target fuel cell inlet air pressure accompanying the fluctuation | variation of the electric power generation electric current of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 20 Fuel processing apparatus 23 Combustion part 25 Reforming part 30 Fuel cell 40 Control apparatus 41 Calculation part 42 Air blower 43 Ammeter 44 Pressure sensor 46 Raw material flow meter 48 Flow meter 54 Power supply air supply line 58 Combustion air Supply line 64 Shutoff valve 68A, 68B Orifice (throttle means)
68GP Throttle means group a Combustion air g Reformed gas m1 Raw material p Anode off gas t Power generation air

Claims (6)

A reforming section that introduces a raw material to reform and generates a reformed gas rich in hydrogen, and a reforming heat that is used for reforming in the reforming section by introducing fuel and combustion air and burning the fuel A fuel processor having a combustion section for generating gas;
A fuel cell that introduces power generation air and the reformed gas, and generates power by an electrochemical reaction between oxygen in the power generation air and hydrogen in the reformed gas;
An anode offgas pipe for introducing an anode offgas containing hydrogen that has not been used for an electrochemical reaction in the fuel cell to the combustion section as the fuel;
Air supply means for supplying the combustion air to the combustion section and supplying the power generation air to the fuel cell;
Combustion air flow rate detection means for detecting the flow rate of combustion air introduced into the combustion section;
Combustion air flow rate adjusting means for adjusting the flow rate of combustion air introduced into the combustion section;
Fuel flow rate grasping means for grasping the flow rate of combustible components in the fuel introduced into the combustion section;
A control device for controlling the combustion air flow rate adjusting means so that a ratio of a flow rate of oxygen in the combustion air to a flow rate of combustible components in the fuel becomes a predetermined ratio in the combustion section ;
Power generation air flow rate detection means for detecting the flow rate of power generation air introduced into the fuel cell;
A generated current detection means for detecting a generated current in the fuel cell;
Wherein the controller controls the air supply means so that the oxygen utilization in the fuel cell becomes the first predetermined utilization rate;
A combustion air supply line for guiding the combustion air discharged from the air supply means to the combustion section;
A plurality of throttle means having different pressure losses, further comprising a throttle means group configured in parallel with each other on the combustion air supply line;
The air supply means comprises a device for discharging air by rotation of a motor;
The combustion air flow rate adjusting means includes a rotation speed adjusting means for adjusting a rotation speed of the motor and the throttle means group;
The control device adjusts the rotation speed of the motor so that the ratio of the flow rate of the combustion air in the combustion section to the flow rate of the fuel becomes a predetermined air ratio, and the oxygen utilization rate in the fuel cell is the first. The throttling means for flowing the combustion air is determined from the plurality of throttling means so as to achieve a predetermined utilization rate of 1;
Fuel cell system. A raw material flow meter for detecting the flow rate of the raw material introduced into the reforming section;
The flow rate of the combustible component in the anode off-gas introduced into the combustion part is calculated from the flow rate of the raw material detected by the raw material flow meter and the generated current of the fuel cell detected by the generated current detection means. An arithmetic unit;
The fuel flow rate grasping means comprises the raw material flow meter, the generated current detection means, and the calculation unit;
The fuel cell system according to claim 1. A power generation air supply line for guiding the power generation air discharged from the air supply means to the fuel cell;
A shutoff valve disposed in the power generation air supply line and capable of shutting off the flow of power generation air in the power generation air supply line;
The fuel cell system according to claim 1 or 2 . The combustion air flow rate detection means is a flow meter;
The fuel cell system according to any one of claims 1 to 3 . A calculation unit for obtaining the flow rate of the power generation air from the pressure of the power generation air introduced into the fuel cell;
The power generation air flow rate detection means includes a pressure detector for detecting the pressure of the power generation air introduced into the fuel cell and the calculation unit;
The fuel cell system according to any one of claims 1 to 4. The calculation unit is introduced into the fuel cell when the power generation current of the fuel cell and the power generation air at a flow rate for generating the power generation current are introduced into the fuel cell at a second predetermined oxygen utilization rate. The relationship with the steady fuel cell inlet air pressure, which is the pressure of the power generation air, is stored in advance;
Further, the calculation unit is configured to generate a target pressure of power generation air introduced into the fuel cell from a fuel cell resistance coefficient that fluctuates following a variation in the power generation current of the fuel cell and the steady fuel cell inlet air pressure. Configured to calculate a target fuel cell inlet air pressure;
The controller is configured to control the air supply means such that the pressure detected by the pressure detector becomes the target fuel cell inlet air pressure;
The fuel cell system according to claim 5 .

Images