JP5401170B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system having a solid oxide fuel cell and a reformer.

  As a fuel cell system, a solid oxide fuel cell system will be described as an example. In this system, a fuel cell having a solid oxide electrolyte membrane and an anode off-gas discharged from the anode of the fuel cell are heated to a reforming temperature region by burning with combustion air to reform the fuel material. A reformer that generates anode gas, and a housing that houses the fuel cell 1 and the reformer. According to this, a system is disclosed that changes the power generation conditions of a fuel cell each time the properties (fuel, composition, etc.) of the fuel material are different (Patent Document 1).

JP 2006-49056 A

  However, even in the above-described system, the power generation output of the fuel cell may fluctuate when the temperature of the outside air serving as the cathode gas changes.

  The present invention has been made in view of the above circumstances, and provides a fuel cell system that is advantageous for stabilizing the power generation output of a fuel cell even when the temperature of the outside air serving as the cathode gas changes. This is the issue.

  The inventor has been eagerly developing a fuel cell system. An output correlator having a strong correlation with the power generation output of the fuel cell exists, and even if there is a fluctuation in the temperature of the outside air, the fuel is maintained so that the temperature of the output correlator is maintained in a substantially constant range. It has been found that adjusting the flow rate of the raw material or the flow rate of combustion air is advantageous for stabilizing the power generation output of the fuel cell, and the present invention has been completed.

That is, a fuel cell system according to the present invention comprises (i) a fuel cell having an anode to which anode gas is supplied and a cathode to which cathode gas is supplied; and (ii) anode off-gas discharged from the fuel cell for combustion. A reformer that is heated to a reforming temperature region by burning with air and reforms the fuel material to generate anode gas; and (iii) an output correlator having a correlation with the power generation output of the fuel cell. A first temperature sensor that detects the temperature; (iv) a second temperature sensor that detects the outside air temperature as the temperature of the cathode gas sucked into the cathode gas carrier that supplies the cathode gas to the cathode of the fuel cell; and (v) the fuel. A control unit that controls the power generation operation of the battery, and (vi) a housing that houses the fuel cell, the reformer, the first temperature sensor, and the control unit,
(Vii) The control unit detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is higher than the reference temperature by the second temperature sensor, and the temperature of the output correlation unit is When the condition that the first temperature sensor detects that the temperature is higher than the threshold temperature is satisfied, a fuel material reduction operation for reducing the supply flow rate of the fuel material supplied to the reformer is executed. By executing the control to suppress the temperature rise of the output correlation unit,
And (viii) the control unit detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is lower than its reference temperature by the second temperature sensor, Combustion air reduction operation for reducing the supply flow rate of combustion air for burning the anode off gas when the condition that the first temperature sensor detects that the temperature is lower than the threshold temperature is satisfied. Is executed to suppress the amount of heat that the anode off gas and the combustion exhaust gas of the combustion air exhaust to the outside of the casing, thereby executing a control that suppresses a decrease in the temperature of the output correlation unit.

  According to the present invention, the operating temperature of the fuel cell is preferably 300 ° C. or higher or 400 ° C. or higher, and examples of the fuel cell include a solid oxide form, a phosphoric acid form, and a molten carbonate form. The upper limit of the operating temperature is exemplified by 1200 ° C and 1000 ° C. The operating temperature refers to the temperature of the electrolyte when the fuel cell performs a rated steady power generation operation. In the present specification, unless otherwise specified, the flow rate means a flow rate per unit time, and the heat amount means a heat amount per unit time.

  According to the fuel cell system, there exists an output correlation unit having a strong correlation with the power generation output of the fuel cell. The temperature of the output correlation unit has a strong influence on the power generation output of the fuel cell. Examples of such an output correlation unit include the temperature of the fuel cell and the temperature in the vicinity of the fuel cell. Therefore, in order to stabilize the power generation output of the fuel cell, it is preferable to stabilize the temperature of the output correlation unit even if the temperature of the outside air changes.

  According to the present invention, when both of the following conditions (a) and (b) are satisfied, the control unit executes the fuel material reduction operation for reducing the supply flow rate of the fuel material, whereby the output correlation unit The control which suppresses the raise of temperature T1 of this is performed, and stabilization of temperature T1 of an output correlation part is aimed at. If the supply flow rate of the fuel material is decreased as described above, the fuel material consumption in the system is reduced, and the fuel cost is reduced while the power generation output is maintained. Here, since the temperature T1 of the output correlation unit is stabilized, the power generation output (power generation voltage) of the fuel cell is stably maintained.

  (A) The second temperature sensor detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is higher than its reference temperature. (B) The first temperature sensor detects that the temperature T1 of the output correlation unit is higher than the threshold temperature.

  Here, the reference temperature of the cathode gas before being supplied to the cathode of the fuel cell may be a pinpoint temperature or a temperature region having a temperature range. The temperature range of the reference temperature of the cathode gas is appropriately selected according to the system, and is exemplified in the range of 1 to 50 ° C, in the range of 2 to 40 ° C, or in the range of 5 to 30 ° C.

  The threshold temperature of the temperature T1 of the output correlation unit may be a pinpoint temperature or a temperature region having a temperature range. The temperature width of the threshold temperature of the temperature T1 is appropriately selected according to the system, and examples include a range of 10 to 100 ° C, a range of 15 to 70 ° C, or a range of 20 to 60 ° C.

  According to the present invention, even if the temperature T1 of the output correlation unit rises above the threshold temperature due to fluctuations in the temperature of the outside air, the temperature T1 of the output correlation unit is stably maintained near the predetermined set temperature. Therefore, a large fluctuation in the power generation output of the fuel cell is suppressed, and the power generation output (power generation voltage) of the fuel cell is stabilized.

  When both of the following conditions (c) and (d) are satisfied, the control unit executes a combustion air reduction operation for reducing the supply flow rate of combustion air for burning the anode off gas. This suppresses the amount of heat that the anode off gas and the combustion exhaust gas of the combustion air exhaust to the outside of the housing. As a result, control for suppressing a decrease in temperature of the output correlation unit is executed.

  (C) The second temperature sensor detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is lower than its reference temperature. (D) The first temperature sensor detects that the temperature T1 of the output correlation unit is lower than the threshold temperature.

  As a result, even if the temperature T1 of the output correlator decreases below the threshold temperature due to fluctuations in the temperature of the outside air, the amount of heat that the exhaust gas of combustion air discharges to the outside is suppressed. For this reason, the fall of the temperature of a fuel cell is suppressed and the fall of temperature T1 of an output correlation part is suppressed. As a result, the temperature T1 of the output correlation unit is maintained near a predetermined set temperature, a large fluctuation in the power generation output of the fuel cell is suppressed, and the power generation output of the fuel cell is stabilized.

  According to the present invention, even when the temperature of the outside air serving as the cathode gas before being supplied to the cathode of the fuel cell is changed, the power generation of the medium-temperature or high-temperature operation type fuel cell such as the solid oxide type A fuel cell system advantageous in stabilizing the output can be provided.

1 is a diagram schematically showing an entire fuel cell system according to Embodiment 1. FIG. 1 is a diagram illustrating a concept of a fuel cell device according to Embodiment 1. FIG. 1 is a cross-sectional view of a fuel cell device according to Embodiment 1. FIG. 10 is a flowchart executed by a control unit according to the second embodiment.

  According to the present invention, the second temperature sensor detects the temperature of the cathode gas sucked into the cathode gas transport source that supplies the cathode gas to the cathode of the fuel cell. In this case, the second temperature sensor preferably detects the temperature of the cathode gas (air) in the housing.

  According to the present invention, the flow rate of the fuel raw material supplied to the reforming unit includes the flow rate of the anode gas used in the power generation reaction at the anode of the fuel cell and the flow rate at which the anode off gas forms a combustion flame in the combustion space. Is preferably set. Similarly, the combustion air for burning the anode off gas in the combustion space is supplied to the combustion space so as to send oxygen in excess of the air-fuel ratio of combustion in the combustion space. In addition, when the cathode off gas becomes combustion air, the flow rate of the cathode gas supplied to the fuel cell includes the flow rate used in the power generation reaction at the cathode of the fuel cell and the cathode off gas for combustion in the combustion space. It is preferable that a flow rate obtained by adding a flow rate for forming a combustion flame as air and a surplus flow rate is set.

  Preferably, the combustion air is a cathode off gas exhausted from the cathode of the fuel cell. The cathode off gas is a gas after the cathode gas undergoes a power generation reaction in the fuel cell. Thus, the cathode off gas contains residual oxygen. The anode off gas is a gas after the anode gas undergoes a power generation reaction in the fuel cell. Therefore, the anode off gas contains a combustible component.

  According to a preferred embodiment of the present invention, the control unit reduces the flow rate of the steam and / or reformed water supplied to the reforming unit when the fuel feed rate reduction operation for reducing the feed rate of the fuel feed rate is performed. Reduce than before performing the operation. The heat of vaporization of the reforming water is large and affects the temperature of the reforming section. Since the flow rate of the reforming water is reduced, excessive cooling of the fuel cell can be suppressed. As a result, an excessive decrease in the temperature T1 of the output correlation unit can be suppressed. Furthermore, the flow rate of steam and / or reformed water supplied to the reforming section is also reduced along with a decrease in the fuel feed rate, so that the S / C value (steam / carbon) is in a substantially constant range. Maintained. Therefore, coking and overcooling in the reforming section are suppressed.

  According to a preferred embodiment of the present invention, the control unit maintains the flow rate of the fuel material before the combustion air reduction operation when performing the combustion air reduction operation for reducing the supply flow rate of the combustion air. Since the flow rate of the fuel raw material is maintained in this way, the flow rate of the anode gas supplied to the fuel cell is favorably maintained, and the power generation output of the fuel cell is favorably maintained. Further, since the flow rate of the anode off gas is maintained, the amount of heat of the combustion flame that heats the reformer is also maintained well, and the reforming reaction in the reformer is maintained well.

(Embodiment 1)
This embodiment is applied to a solid oxide fuel cell system. FIG. 1 shows the concept of a solid oxide fuel cell system. As shown in FIG. 1, the fuel cell system basically includes a solid oxide fuel cell 1, a reformer 2, a first temperature sensor 101, a second temperature sensor 102, and a control unit 100. And a housing 9. Further, the fuel cell system includes a reforming water system 4, a fuel material supply system 5, a cathode gas supply thread 6, and a hot water storage system 7 inside the housing 9. 1 and 2, the fuel cell 1 is schematically shown.

As shown in FIG. 2, the plurality of fuel cells 1 are juxtaposed via a passage 32 r of a power generation chamber 32 to which a cathode gas is supplied to form a stack. The fuel cells are electrically connected by a current collector (not shown). The fuel cell 1 includes a porous conductive portion 11w having a passage 11r through which an anode gas flows, an anode 11 that functions as a fuel electrode, a cathode 12 that functions as an oxidant electrode facing the passage 32r to which a cathode gas is supplied, It has an electrolyte membrane 15 using a solid oxide sandwiched between an anode 11 and a cathode 12 as a base material, and a dense connector 10x. The solid oxide has a property of conducting oxygen ions (O ²⁻ ), and examples thereof include zirconia type such as YSZ and lanthanum gallate type. The anode 11 is exemplified by nickel-ceria cermet. Examples of the cathode 12 include samarium cobaltite and lanthanum manganite. The material is not limited to the above. An anode gas manifold 13 that guides the anode gas to the inlet of the fuel cell 1 is disposed below the fuel cell 1.

As shown in FIG. 1, the reformer 2 includes an evaporation unit 20 and a reforming unit 22 to which a fuel material is supplied. The evaporator 20 vaporizes the liquid phase reformed water supplied from the reforming water system 4 to the evaporator 20. The reforming unit 22 is provided downstream of the evaporation unit 20 and steam-reforms the fuel material with the steam generated by the evaporation unit 20 to generate anode gas. The anode gas is hydrogen gas or hydrogen-containing gas. In the housing 9, the hot module 3 (power generation module) having an outside air inlet 92 that allows the housing chamber 91 of the housing 9 to communicate with the outside air is housed inside the housing 9, and forms a power generation chamber 32. A container-like heat insulating portion 30 formed of a heat insulating material is provided, and the fuel cell 1 and the reformer 2 are accommodated inside the heat insulating portion 30 via a combustion space 23. In the hot module 3, the reformer 2 (the reforming unit 22 and the evaporation unit 20) is disposed on the upper side of the fuel cell 1. In the hot module 3, a combustion space 23 is formed between the fuel cell 1 and the reformer 2 (the reforming unit 22 and the evaporation unit 20). In particular, a combustion space 23 is formed between the upper part of the fuel cell 1 and the lower part of the reformer 2 (the reforming part 22 and the evaporation part 20). The anode off gas discharged from the anode 11 of the fuel cell 1 is discharged into the combustion space 23. The anode off gas means a gas discharged from the fuel cell 1 and contains unreacted hydrogen (combustible component) and can be combusted. The cathode off gas contains unreacted oxygen.

  The anode off-gas discharged to the combustion space 23 is burned by cathode gas or cathode off-gas (corresponding to combustion air), and a combustion flame 24 is formed in the combustion space 23. The gas that forms the combustion flame 24 in the combustion space 23 becomes combustion exhaust gas. The combustion flame 24 in the combustion space 23 heats both the reforming unit 22 and the evaporation unit 20 and maintains the temperature of the reforming unit 22 in the reforming reaction temperature region.

  As shown in FIG. 1, the reforming water system 4 supplies reforming water that is consumed as water vapor in steam reforming in the reforming unit 22 to the reforming unit 22. 2, a reforming water passage 41, a reforming water pump 42 (reforming water transport source), and a water supply valve 43. The water purifier 40 includes a water purification material 40a such as an ion exchange resin that can purify water. The reforming water passage 41 is provided with a water storage tank 44, a reforming water pump 42, and a water supply valve 43.

  As shown in FIG. 1, the fuel material supply system 5 includes a fuel material supply passage 51 connected to a fuel source 50 for supplying a fuel material such as a hydrocarbon system to the reformer 2, an inlet valve 52, a flow meter. 53, a desulfurizer 54, and a fuel feed pump 55 (fuel feed transfer source). In the fuel material supply passage 51, an inlet valve 52, a flow meter 53, a desulfurizer 54, and a fuel material pump 55 are provided. The cathode gas supply yarn 6 includes a cathode gas supply passage 60 for supplying a cathode gas, which is air, to the cathode 12 of the fuel cell 1, a dust filter 61, a cathode gas pump 62 (cathode gas transport source), and a flow meter 63. Have. A dust filter 61, a cathode gas pump 62, and a flow meter 63 are disposed in the cathode gas supply passage 60. The dust filter 61 is disposed in the housing chamber 91 of the housing 9.

  When the cathode gas pump 62 is driven, outside air flows into the housing chamber 91 from the outside air inlet 92 and is supplied to the cathode 12 from the inlet of the fuel cell 1 as cathode gas through the dust filter 61 and the cathode gas supply passage 60. A second temperature sensor 102 that detects the temperature of the outside air (cathode gas) taken in from the outside air inlet 92 is provided in the vicinity of the outside air inlet 92 of the housing 9. The second temperature sensor 102 detects the temperature of the cathode gas before being supplied to the cathode 12 of the fuel cell 1. That is, the second temperature sensor 102 is the cathode gas before being sucked into the cathode gas pump 62 supplied to the cathode 12 of the fuel cell 1, specifically, the temperature of the air that is the cathode gas in the housing 9, in particular, The temperature of the cathode gas (air) in the vicinity of the outside air inlet 92 in the inside of the housing 9 is detected. Since the temperature near the outside air inlet 92 substantially corresponds to the temperature of the outside air, the outside air temperature outside the housing 9 is substantially detected. A signal detected by the second temperature sensor 102 is input to the control unit 100. The control unit 100 includes an input processing circuit, an output processing circuit, a CPU, and a memory.

  As shown in FIG. 1, the hot water storage system 7 includes a circulation passage 71 that circulates through the heat exchanger 74 and the hot water storage tank 70, and a hot water storage pump 72 (a hot water supply source) provided in the circulation passage 71. When the hot water storage pump 72 is operated, the water in the hot water storage tank 72 is supplied from the circulation passage 71 to the heat exchanger 74 and heated by heat exchange with the combustion exhaust gas in the heat exchanger 74. The heated water returns to the hot water storage tank 70. Thereby, the hot water storage tank 70 stores hot water. A heat exchanger 74 is provided in the vicinity of the hot module 3. The heat exchanger 74 has a gas passage 74g through which the combustion exhaust gas discharged from the hot module 3 passes and a water passage 74w through which water in the circulation passage 71 of the hot water storage system 7 passes. The heat of the combustion exhaust gas flowing through the heat exchanger 74 is transmitted to the water in the circulation passage 71 of the hot water storage system 7. An exhaust passage 75 extends from the gas passage 74 g of the heat exchanger 74 toward the exhaust port 76 of the housing 9, and the combustion exhaust gas is exhausted from the exhaust port 76 through the exhaust passage 75. A condensed water passage 77 extends from the gas passage 74 g of the heat exchanger 74 toward the water purifier 40. Accordingly, the water vapor in the vapor phase contained in the combustion exhaust gas is cooled in the heat exchanger 74 to generate condensed water. The condensed water is supplied from the condensed water passage 77 to the water purifier 40.

  Before starting the power generation operation of the fuel cell 1, the fuel material pump 55 is driven, and the fuel material is supplied to the fuel cell 1 through the desulfurizer 54, the fuel material supply passage 51, the evaporation unit 20 and the reforming unit 22. And supplied to the combustion space 23 via the fuel cell 1. Further, since the cathode gas pump 62 is driven, cathode gas (air) is supplied to the combustion space 23 via the cathode 12 of the fuel cell 1. As a result, the combustible fuel material is burned by the cathode gas (air) in the combustion space 23, and a combustion flame 24 is formed in the combustion space 23. The combustion flame 24 heats the reforming unit 22 and the evaporation unit 20 to a high temperature to enable a reforming reaction.

Next, during the power generation operation of the fuel cell 1, the fuel material pump 55 is driven, and the fuel material is supplied to the evaporation unit 20 of the reformer 2 through the fuel material supply passage 51. Further, the reforming water pump 42 is driven, and the reforming water in the water storage tank 44 is supplied to the evaporator 20 through the reforming water passage 41. Here, since the evaporation unit 20 is heated, the evaporation unit 20 vaporizes the reformed water. The steam is supplied to the reforming unit 22. The reforming unit 22 steam reforms the fuel material to generate anode gas. When the fuel raw material is methane-based, it is considered that the generation of the anode gas in the steam reforming is based on the following equation (1). In the solid oxide fuel cell 1, CO can be used as fuel in addition to H ₂ .

(1) ... CH ₄ + 2H ₂ O → 4H ₂ + CO ₂
CH ₄ + H ₂ O → 3H ₂ + CO
The generated anode gas is supplied to the inlet of the anode 11 of the fuel cell 1 through the anode gas passage 14 and the anode gas manifold 13 and used for power generation. Since the cathode gas pump 62 is driven, outside air outside the housing 9 is supplied as cathode gas to the inlet of the cathode 12 of the fuel cell 1 through the dust filter 61 and the cathode gas supply passage 60. Thereby, the fuel cell 1 generates electric power.

In the power generation reaction, it is considered that the reaction (2) basically occurs at the anode 11 supplied with the hydrogen-containing gas. It is considered that the reaction (3) basically occurs at the cathode 12 to which oxygen is supplied. Oxygen ions (O ²⁻ ) generated at the cathode 12 conduct the electrolyte from the cathode 12 toward the anode 11.

(2) ... H ₂ + O ²⁻ → H ₂ O + 2e ⁻
When CO is contained, CO + O ²⁻ → CO ₂ + 2e ⁻
(3)... 1 / 2O ₂ + 2e ⁻ → O ²⁻
The anode off-gas and cathode off-gas after the power generation reaction are discharged to the combustion space 23 above the fuel cell 1 to form a combustion flame 24 in the combustion space 23. The burned anode off-gas and cathode off-gas become combustion exhaust gas, and are discharged to the outside of the housing 9 from the exhaust port 76 at the tip of the exhaust passage 75 through the heat exchanger 74 and the relief valve 78. The condensed water in which the moisture contained in the combustion exhaust gas is condensed is supplied to the water purifier 40 from the condensed water passage 77 led out from the heat exchanger 74 and purified by the water purifier 40. The purified water is stored in the water storage tank 44 as reformed water 44w.

  FIG. 3 shows the vicinity of the fuel cell device arranged in the hot module 3. The fuel cell device includes a fuel cell 1 and a reformer 2 on the upper side of the fuel cell 1. As shown in FIG. 2, the fuel cell device includes a base body 80 having a placement chamber 81, a fuel cell 1 housed in the placement chamber 81 of the base body 80, and an anode gas manifold 13 placed at the bottom of the fuel cell 1. The reformer 2 disposed on the upper side of the fuel cell 1 in the arrangement chamber 81 of the base body 80, the combustion space 23 formed between the upper end of the fuel cell 1 and the lower end of the reformer 2, and the fuel cell A heat insulating layer 82 formed of a heat insulating material disposed on the outside of 1, a combustion exhaust gas passage 83 disposed outside the heat insulating layer 82, and a cathode gas passage 84 disposed outside the combustion exhaust gas passage 83. Have

  As shown in FIG. 3, the combustion exhaust gas passage 83 has an inlet 83i on the reformer 2 and combustion space 23 side, and an outlet 83p formed on the lower end side. The cathode gas passage 84 includes a first passage 841 extending in the vertical direction, a second passage 842 extending in the lateral direction from the upper end of the first passage 841, a third passage 843 extending downward from the tip of the second passage 842, And an outlet 845 formed on the lower end side of the third passage 843. Two cell side-by-side groups 1W formed by juxtaposing the fuel cells 1 in the thickness direction are provided so as to sandwich the third passage 843.

  In FIG. 3, the cathode gas (air) flows through the first passage 841, the second passage 842, and the third passage 843 along the arrow C1, arrow C2, arrow C3, arrow C4, and arrow C5 directions. The gas is supplied from the outlet 845 at the tip of the cathode gas passage 84 to the inlet of the lower portion of the cathode 12 of the fuel cell 1 and further used for the power generation reaction of the cathode 12 while passing upward through the cathode 12 of the fuel cell 1. The cathode gas after the power generation reaction is discharged from the upper part of the fuel cell 1 into the combustion space 23 as a cathode off gas. On the other hand, the anode gas is used for the power generation reaction of the anode 11 while passing upward from the anode gas manifold 13 through the anode 11 of the fuel cell 1, and after the power generation reaction, the anode gas is used as an anode offgas from the upper part of the fuel cell 1 for combustion. 23 is discharged.

  FIG. 2 is a conceptual diagram in the vicinity of the fuel cell 1 and the reformer 2. As described above, the anode off gas is discharged from the upper part of the anode 11 of the fuel cell 1 into the combustion space 23, the cathode off gas discharged from the cathode 12 is discharged into the combustion space 23, and the anode off gas is burned by the cathode off gas. A combustion flame 24 is formed, and the reforming unit 22 and the evaporation unit 20 are heated.

  Therefore, the flow rate of the anode gas (fuel material) includes the flow rate used in the power generation reaction in the anode 11 of the fuel cell 1, the flow rate at which the anode off gas forms the combustion flame 24 in the combustion space 23, and the surplus flow rate. The added flow rate is set. As the flow rate of the cathode gas, the flow rate used in the power generation reaction at the cathode 12 of the fuel cell 1, the flow rate at which the cathode off-gas forms the combustion flame 24 as combustion air in the combustion space 23, and the marginal flow rate. The added flow rate is set.

  Now, according to the system in which the solid oxide fuel cell 1 is mounted, the operating temperature of the fuel cell 1 in the steady operation is in the range of 400 to 1100 ° C and in the range of 500 to 800 ° C. An output correlation unit 200 having a strong correlation with the power generation output of the solid oxide fuel cell 1 is present in the hot module 3. Such an output correlation unit 200 is preferably the fuel cell 1 or the vicinity of the fuel cell 1. Specifically, in FIG. 3, it is preferable that the output correlation unit 200 be located at the outlet 845 or in the vicinity of the outlet 845 in the third passage 843 of the cathode gas passage 84. The temperature T1 of the output correlation unit 200 is detected by the first temperature sensor 101 embedded in the hot module 3. A signal from the first temperature sensor 101 is input to the control unit 100.

  The temperature T1 of the output correlation unit 200 has a strong influence on the power generation output of the solid oxide fuel cell 1. When the temperature T1 of the output correlator 200 fluctuates by ΔT (for example, 20 ° C.) in the positive direction or fluctuates by ΔT (for example, 20 ° C.) in the negative direction, the power generation output of the fuel cell 1 varies greatly. Therefore, in order to stabilize the power generation output of the fuel cell 1, it is preferable to stabilize the temperature T1 of the output correlation unit 200 as much as possible. This embodiment stabilizes the power generation output of the fuel cell 1 by stabilizing the temperature T1 of the output correlation unit 200 as much as possible even if there is a large temperature change in the outside air, in particular, stabilizes the power generation voltage, The goal is to maintain the power generation efficiency of the fuel cell 1 high.

  According to this embodiment, the reference temperature Ts of the temperature Tc of the cathode gas before being supplied to the cathode 12 of the fuel cell 1 is set in advance. The reference temperature Ts can be set based on the average temperature of the outside air during the year in the environment where the system is installed.

  According to the present embodiment, the following conditions (a) and (b) may be satisfied during actual operation of the system. (A) The second temperature sensor 102 detects that the temperature Tc of the cathode gas before being supplied to the cathode 12 of the fuel cell 1 is higher than the reference temperature Ts. (B) The condition that the first temperature sensor 101 detects that the temperature T1 of the output correlation unit 200 is higher than the threshold temperature is satisfied.

  As described above, when both conditions (a) and (b) are satisfied under the influence of the temperature of the outside air (corresponding to the cathode gas before the power generation reaction), the cathode gas formed in the outside air This means that the temperature T1 of the output correlator 200 is increasing due to the increase in temperature Tc. In this case, the control unit 100 reduces the rotation speed (driving amount) of the fuel feed pump 55 with the target that the temperature T1 of the output correlation unit 200 is maintained at the threshold temperature, and the reforming unit 22 The supply flow rate Qf of the fuel raw material supplied to is reduced. Thereby, the supply flow rate Qf of the fuel raw material supplied to the reforming unit 22 decreases.

  Accordingly, the flow rate of the anode gas generated in the reforming unit 2 is reduced. As a result, the flow rate of the anode off-gas discharged from the anode 11 of the fuel cell 1 to form the combustion flame 24 is reduced, the amount of heat of the combustion flame 24 is reduced, and as a result, an excessive increase in the temperature T1 of the output correlation unit 200 is suppressed. Is done. As a result, an excessive increase in the temperature T1 of the output correlator 200 is suppressed, and the temperature T1 is stabilized. When the supply flow rate Qf of the fuel raw material supplied to the reforming unit 22 is decreased, the water vapor supplied to the reforming unit 22 is also decreased accordingly, and the value of S / C (team / carbon) is made to be in a substantially constant range. It is preferable to maintain. Therefore, it is preferable to reduce the rotational speed of the reforming water pump 42 as the fuel material supply flow rate Qf is reduced. In the present specification, unless otherwise specified, the flow rate means a flow rate per unit time. The number of rotations means the number of rotations per unit time.

  As described above, if the supply flow rate Qf of the fuel material supplied to the reforming unit 22 is decreased, the consumption amount of the fuel material in the system is reduced, the fuel cost is reduced, and the power generation cost is expected to be reduced. Moreover, since the stability of the temperature T1 of the output correlation unit 200 is high, the temperature T1 of the output correlation unit 200 is prevented from greatly decreasing or increasing, and the power generation output of the fuel cell 1 (particularly the generated voltage) is suppressed. ) Is stably maintained.

  As a result, even if the temperature T1 of the output correlation unit 200 rises above the threshold temperature, the temperature T1 of the output correlation unit 200 is stably maintained near a predetermined set temperature. For this reason, even if the outside air temperature decreases and the cathode gas temperature Tc decreases, a large fluctuation in the power generation output of the fuel cell 1 is suppressed, the power generation output of the fuel cell 1 is stabilized, and the power generation efficiency is maintained high. .

  In actual operation of the system, both the following conditions (c) and (d) may be satisfied.

  (C) The temperature of the cathode gas (the cathode gas before being supplied to the cathode gas pump 62 and the cathode 12 of the fuel cell 1) taken in from the outside air inlet 92 is lower than the reference temperature Ts. 2 To be detected by the temperature sensor 102. (D) The condition that the first temperature sensor 101 detects that the temperature T1 of the output correlation unit 200 is lower than the threshold temperature is satisfied.

  Thus, under the influence of the temperature of the outside air (corresponding to the cathode gas before being sucked into the cathode gas pump 62), when both the conditions (c) and (d) are satisfied, the temperature Tc of the cathode gas It means that the temperature T1 of the output correlation unit 200 is decreased due to the decrease.

  When both of the above conditions (c) and (d) are satisfied, the control unit 100 determines the cathode gas (corresponding to the cathode offgas and corresponding to the combustion air) before being supplied to the fuel cell 1. The supply flow rate Qc is decreased, and consequently the flow rate of the cathode off gas after the power generation reaction discharged from the cathode 12 of the fuel cell 1 is decreased. As a result, the flow rate of the combustion exhaust gas (the anode off gas corresponding to the exhaust gas combusted with the cathode off gas) discharged from the combustion space 23 through the exhaust passage 75 is reduced.

  Thereby, the amount of heat exhausted from the combustion exhaust gas to the outside of the hot module 3 and the housing 9 is suppressed. As a result, the amount of heat released to the outside of the system together with the combustion exhaust gas is reduced, and a decrease in the temperature T1 of the output correlation unit 200 is suppressed. In this case, it is preferable not to increase the supply flow rate Qf of the fuel material supplied to the reforming unit 22 even if the temperature T1 of the output correlation unit 200 is lower than the threshold temperature. That is, the control unit 100 reduces the supply flow rate Qc of the cathode gas (corresponding to combustion air) supplied to the cathode 12 of the fuel cell 1 so that the cathode off-gas, that is, the combustion exhaust gas discharged from the cathode 12 is discharged to the outside. Reduce the amount of heat discharged. Thereby, a decrease in the temperature of the fuel cell 1 is suppressed, and a decrease in the temperature T1 of the output correlation unit 200 is suppressed.

  According to the present embodiment, as described above, even if the temperature T1 of the output correlation unit 200 is lower than the threshold temperature, the flow rate Qc of the cathode gas supplied to the cathode 12 of the fuel cell 1 is reduced. The flow rate of the cathode off gas per unit time is reduced, and as a result, the amount of heat exhausted from the combustion exhaust gas is suppressed. For this reason, a decrease in the temperature of the fuel cell 1 and the temperature T1 of the output correlation unit 200 is suppressed, the temperature T1 of the output correlation unit 200 is maintained near a predetermined set temperature, and a large fluctuation in the power generation output of the fuel cell 1 is suppressed. Thus, the power generation output of the fuel cell 1 is stable and the power generation efficiency is maintained high.

(Embodiment 2)
FIG. 4 shows a second embodiment. This embodiment has basically the same configuration as that of the first embodiment, and has the same functions and effects. FIG. 4 shows a flowchart executed by the CPU of the control unit 100. According to the present embodiment, the reference temperature Ts of the cathode gas before being supplied to the cathode 12 of the fuel cell 1 is set to a high temperature side reference temperature Ts1 (for example, 35 ° C.) and a low temperature in consideration of the installation environment of the system. A side reference temperature Ts2 (for example, 25 ° C.) is set. As the threshold temperature Tp of the temperature T1 detected by the first temperature sensor 101, a threshold temperature Tp1 (eg, 700 ° C.) and a threshold temperature Tp2 (eg, 650) are set.

  First, the control unit 100 determines whether or not the fuel cell 1 is in a steady power generation operation (step S102). If it is a steady power generation operation, the signals of the first temperature sensor 101 and the second temperature sensor 102 are read (step S104). Next, the control unit 100 determines whether or not the cathode gas temperature Tc detected by the first temperature sensor 101 is higher than its reference temperature Ts1 (for example, 35 ° C.). That is, it is determined whether or not the temperature of the cathode gas formed by the outside air is high (step S106). If the temperature Tc of the cathode gas, which is the outside air, rises higher than the reference temperature Ts1 (for example, 35 ° C.), the above condition (a) is satisfied (YES in step S106). It is determined whether or not the temperature T1 of the output correlation unit 200 detected by the temperature sensor 101 is higher than the threshold temperature Tp1 (step S108). If the temperature T1 of the output correlation unit 200 is higher than the threshold temperature Tp1 (for example, 700 ° C.), the above condition (b) is satisfied (YES in step S108). Both the above conditions (a) and (b) are satisfied.

  In this case, it means that the temperature T1 of the output correlator 200 is increased due to the increase in the temperature Tc of the cathode gas that is outside air. In this case, the control unit 100 outputs a command for reducing the supply flow rate Qf of the fuel material supplied to the reforming unit 22 (step S110). Further, the control unit 100 outputs a command for reducing the rotational speed Nf (driving amount) of the fuel material pump 55 than when the temperature T1 has not risen (step S112).

  As a result, the temperature T1 of the output correlation unit 200 is easily maintained near the threshold temperature Tp1 (for example, 700 ° C.). That is, since the supply flow rate Qf of the fuel raw material supplied to the reforming unit 22 is reduced in this way, the flow rate of the anode off gas discharged from the anode 11 of the fuel cell 1 and forming the combustion flame 24 is reduced. As a result, the amount of heat of the combustion flame 24 decreases, and as a result, an excessive increase in the temperature T1 of the output correlation unit 200 is suppressed. As a result, an excessive increase in the temperature T1 of the output correlator 200 is suppressed, and the temperature T1 is stabilized.

  Note that when the supply flow rate Qf of the fuel material supplied to the reforming unit 22 is decreased, the rotation speed Nw of the reforming water pump 42 is decreased (step S114). Thereby, the flow volume of the reforming water supplied to the evaporation part 20 decreases. Therefore, the flow rate of water and / or steam supplied to the reforming unit 22 is reduced accordingly. Therefore, the value of S / C (team / carbon) is maintained in a substantially constant range.

  When both of the above (a) and (b) are not satisfied, the process proceeds to step S120, and the temperature of the cathode gas that is the outside air taken in from the outside air inlet 92 of the housing 9 is the reference temperature Ts2 (for example, The controller 100 determines whether the second temperature sensor 102 detects that the temperature is lower than 25 ° C.) (step S120). That is, the control unit 100 determines whether or not the temperature of the outside air is low (Step S120). Here, if the temperature of the cathode gas is lower than the reference temperature Ts2 (for example, 25 ° C.) and the temperature of the outside air is low (YES in step S120), the temperature T1 of the output correlator 200 is set next. The controller 100 determines whether or not the first temperature sensor 101 detects that the temperature is lower than the threshold temperature Tp2 (for example, 650 ° C.) (step S122).

  Here, if the temperature T1 of the output correlation unit 200 is lower than the threshold temperature Tp2 (for example, 650 ° C.) (YES in step S122), both conditions (c) and (d) described above are satisfied. Will be. In this case, the control unit 100 outputs a command for maintaining the supply flow rate Qf of the fuel material supplied to the reforming unit 22 (step S124). Thereby, the flow rate of the anode gas supplied to the fuel cell 1 is maintained. In this case, it is preferable that the control unit 100 maintain the number of revolutions of the reforming water pump 42 in order to maintain the flow rate of the reforming water supplied to the evaporation unit 20. Therefore, the flow rate of the steam supplied to the reforming unit 22 is also maintained, and the S / C value (steam / carbon) is maintained in a substantially constant range.

  Next, the control unit 100 outputs a command to decrease the cathode gas supply flow rate Qc (step S126), and decreases the rotational speed Nc of the cathode gas pump 62 (step S128). The cathode gas becomes cathode offgas after the power generation reaction, and corresponds to combustion air for burning the anode offgas in the combustion space 23. In addition, it waits for a predetermined time (step S130) and suppresses hunting.

  Since the cathode gas flow rate Qc is thus reduced, the cathode offgas flow rate after the power generation reaction is reduced. As a result, the flow rate of the combustion exhaust gas discharged from the combustion space 23 is relatively reduced. As a result, the amount of heat exhausted from the combustion exhaust gas to the outside of the hot module 3 and the housing 9 is suppressed, and a decrease in the temperature T1 of the output correlation unit 200 is suppressed.

  In this case, even if the temperature T1 of the output correlation unit 200 is lower than the threshold temperature Tp2 (for example, 650 ° C.), the control unit 100 sets the supply flow rate Qf of the fuel material supplied to the reforming unit 22. Since it does not increase, the consumption of the fuel raw material is suppressed while maintaining the power generation output. Instead, the supply flow rate Qc of the cathode gas (corresponding to combustion air) supplied to the cathode 12 of the fuel cell 1 is decreased, and the cathode off-gas discharged from the cathode 12, that is, the combustion exhaust gas, is outside the housing 9. The amount of heat to be discharged is reduced. In this way, large fluctuations in the power generation output of the fuel cell 1 are suppressed, the power generation output of the fuel cell 1 is stable, and the power generation efficiency is maintained high.

(Embodiment 3)
This embodiment has basically the same configuration as that of the first embodiment, and has the same functions and effects. The second temperature sensor 102 that detects the temperature of the cathode gas before being supplied to the fuel cell 1 is provided in the housing chamber 91 of the housing 9, for example, near the dustproof filter 61, near the water purifier 40, It is provided in the vicinity of the tank 44. Therefore, the cathode gas temperature Tc detected by the second temperature sensor 102 corresponds to the temperature of the air in the housing chamber 91 of the housing 9.

(Other)
The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope not departing from the gist. The fuel cell 1 has a flat plate side-by-side structure formed by assembling a flat plate anode 11 and a cathode 12, but is not limited thereto, and may be a tube type in which an anode, an electrolyte, and a cathode are wound. In the fuel cell device shown in FIG. 3, the two cell juxtaposed groups 1W are provided so as to sandwich the third passage 843 of the cathode gas passage 84, but the cell juxtaposed group 1W may be one set. The electrolyte of the fuel cell is not limited to the solid oxide form, but may be a phosphoric acid form or a molten carbonate form. The output correlator 200 is a cathode gas passage 84 inside the fuel cell device, but is not limited thereto, and may be the anode gas manifold 13, the anode 11, the cathode 12, or a hot module. 3 heat insulation portions 30 or components in the hot module 3 may be used.

  The present invention can be used in, for example, fuel cell systems for stationary use, vehicles, electronic equipment, and electrical equipment.

  1 is a fuel cell, 11 is an anode, 12 is a cathode, 2 is a reformer, 20 is an evaporation section, 22 is a reforming section, 23 is a combustion space, 24 is a combustion flame, 3 is a hot module, and 4 is reforming Water system, 40 is a water purifier, 41 is a reforming water passage, 42 is a reforming water pump, 44 is a water supply tank, 5 is a fuel material supply system, 51 is a fuel material supply passage, 55 is a fuel material pump, and 6 is a cathode. Gas supply system, 60 is cathode gas supply passage, 62 is cathode gas pump, 7 is hot water storage system, 70 is hot water storage tank, 71 is circulation passage, 72 is hot water storage pump, 74 is heat exchanger, 75 is exhaust passage, 76 is exhaust Mouth, 80 is a base, 9 is a housing, 91 is a storage chamber, 92 is an outside air intake, 100 is a control unit, 101 is a first temperature sensor, 102 is a second temperature sensor, and 200 is an output correlation unit.

Claims (4)

A fuel cell having an anode supplied with an anode gas and a cathode supplied with a cathode gas;
A reformer that is heated to a reforming temperature region by burning the anode off-gas discharged from the fuel cell with combustion air, reforming a fuel material to generate the anode gas;
A first temperature sensor for detecting the temperature of the output correlation unit having a correlation with the power generation output of the fuel cell;
A second temperature sensor that detects an outside air temperature as a temperature of the cathode gas sucked into a cathode gas transport source that supplies the cathode gas to the cathode of the fuel cell;
A control unit for controlling the power generation operation of the fuel cell;
A housing for housing the fuel cell, the reformer, and the first temperature sensor;
The control unit detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is higher than a reference temperature of the cathode gas, and the output correlation unit When the condition that the first temperature sensor detects that the temperature of the fuel is higher than the threshold temperature is satisfied, the fuel decreases the supply flow rate of the fuel material supplied to the reformer By executing the raw material reduction operation, control to suppress the temperature rise of the output correlation unit, and
The control unit detects that the temperature of the cathode gas before being supplied to the cathode of the fuel cell is lower than a reference temperature thereof, the second temperature sensor, the output correlation unit When the condition that the first temperature sensor detects that the temperature of the gas is lower than the threshold temperature is satisfied, the combustion air flow for reducing the supply flow rate of the combustion air for burning the anode off-gas A fuel that performs an air reduction operation and performs control to suppress a decrease in temperature of the output correlation unit by suppressing the amount of heat that the anode off gas and the combustion exhaust gas of the combustion air exhaust to the outside of the housing Battery system.   2. The fuel cell system according to claim 1, wherein the combustion air is a cathode off-gas after a power generation reaction discharged from the cathode of the fuel cell.   The control unit according to claim 1, wherein the control unit sets a flow rate of water vapor and / or reformed water supplied to the reformer when the fuel material reduction operation for reducing the supply flow rate of the fuel raw material is performed. A fuel cell system that reduces the amount of fuel before it is performed.   4. The fuel material according to claim 1, wherein the control unit performs the combustion air reduction operation for reducing a supply flow rate of the combustion air before performing the combustion air reduction operation. 5. Cell system that maintains the flow rate of

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