JP7359029B2 - fuel cell system - Google Patents

Description

The present disclosure relates to fuel cell systems.

Conventionally, functional products such as fuel pumps are placed in the raw fuel path through which raw fuel such as city gas flows, and a reformer is placed downstream of the functional product to reform the raw fuel and generate reformed fuel. A fuel cell system is known (for example, see Patent Document 1). The reformed fuel produced by the reformer is supplied to the fuel cell and reacts with the oxidant gas inside the fuel cell, thereby outputting electrical energy from the fuel cell. The off-gas fuel and off-gas air discharged from the fuel cell are then supplied to the combustor and burned.

In the fuel cell system described in Patent Document 1, a circulation path branched from a reformed fuel path connecting a reformer and a fuel cell is connected upstream of a functional product in the raw fuel path. As a result, a portion of the reformed fuel flowing through the reformed fuel path returns to the upstream side of the functional product in the raw fuel path via the circulation path.

Japanese Patent Application Publication No. 2018-195570

By the way, steam reforming when producing reformed fuel in a reformer is an endothermic reaction, and the reforming rate improves under high temperature conditions. Therefore, in order to improve the performance of the reformer, it is effective to heat the reformer with the heat of the combustor.

However, if the reformer is heated with heat from the combustor, the amount of reformed fuel consumed by the fuel cell will decrease due to a drop in power demand on the load side, for example, and the hydrogen concentration of the off-gas fuel will increase. , the temperature of the combustor becomes high, and the amount of heating of the reformer by the combustor increases. In this case, the temperature of the reformed fuel produced in the reformer becomes higher than normal, and the high-temperature reformed fuel reaches the functional product via the circulation path. This is undesirable because, for example, if the functional product has low heat resistance, it may cause malfunction of the functional product.

The present disclosure provides a fuel cell system that includes a circulation path that returns a portion of the reformed fuel upstream of a functional product in a raw fuel path, in which high-temperature reformed fuel is supplied to the functional product via the circulation path and the functional product is The purpose is to prevent malfunctions from occurring.

The invention according to claims 1 , 2, and 3 ,
A fuel cell system,
a reformer (34) that generates reformed fuel by reforming raw fuel input from the outside;
a fuel cell (10) that outputs electrical energy through an electrochemical reaction between the reformed fuel generated in the reformer and the oxidizing gas;
a combustor (73) that burns off-gas fuel and off-gas air discharged from the fuel cell;
A raw fuel path (30A) that flows the raw fuel toward the reformer;
Functional products (32, 33) provided upstream of the reformer in the raw fuel route,
a reformed fuel path (30B) that flows the reformed fuel generated in the reformer to the fuel cell;
a circulation path (60) that returns a portion of the reformed fuel flowing through the reformed fuel path to the upstream of the functional product in the raw fuel path;
a flow rate adjustment member (61) that adjusts the flow rate of reformed fuel flowing through the circulation path;
A control device (100) that controls a flow rate adjustment member,
The reformer is designed to transfer heat from the combustor,
When the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature, the control device controls the flow rate adjusting member to throttle the flow rate of the reformed fuel returned from the circulation path to the raw fuel path.
In the invention according to claim 1, the control device is configured to reduce the amount of raw fuel supplied to the reformer when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. Controls a fuel pump (32) that supplies raw fuel to the reformer.
In the invention according to claim 2, the control device is configured to increase the amount of oxidant gas supplied to the fuel cell when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. Controls an oxidizing gas pump (21) that supplies oxidizing gas to the fuel cell.
The invention according to claim 3 is provided with a heat exchange device (63) for dissipating heat from the reformed fuel flowing through the circulation path, and the raw fuel path includes a heat exchanger (63) that connects the reformed fuel to the raw fuel path from the outside upstream of the connection point with the circulation path. A fuel cutoff member (31) is provided to cut off the introduction of the raw fuel, and the control device is configured to control the heat exchange device to operate normally when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. If the system does not operate normally, the flow rate adjusting member is controlled so that the circulation path is fully closed, and the fuel pump (32) supplies raw fuel to the reformer and the oxidizing gas pump supplies oxidizing gas to the fuel cell. (21) Stop each of them, and further control the fuel cutoff member so that the introduction of raw fuel to the raw fuel path is cut off.

According to this, when the temperature of the reformed fuel returned from the circulation path to the raw fuel path rises above a predetermined temperature, the flow rate of the reformed fuel returned from the circulation path to the raw fuel path is throttled by the flow rate adjustment member. Supply of high-temperature reformed fuel to the functional products via the fuel pump is suppressed. Therefore, it is possible to suppress the occurrence of malfunction of the functional product due to supply of high-temperature reformed fuel to the functional product.

Note that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence between the component etc. and specific components etc. described in the embodiments to be described later.

FIG. 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. 5 is a flowchart illustrating an example of a control process executed by the control device of the fuel cell system according to the first embodiment. It is a schematic block diagram of the fuel cell system of 2nd Embodiment. 7 is a flowchart illustrating an example of a control process executed by a control device of a fuel cell system according to a second embodiment. 7 is a flowchart illustrating an example of a failure diagnosis performed by a control device for a fuel cell system according to a second embodiment. It is a schematic block diagram of the fuel cell system of 3rd Embodiment. 12 is a flowchart illustrating an example of a failure diagnosis performed by a control device for a fuel cell system according to a third embodiment. It is a schematic block diagram of the fuel cell system of 4th Embodiment. 12 is a flowchart illustrating an example of a failure diagnosis performed by a control device for a fuel cell system according to a fourth embodiment. It is a flowchart which shows an example of the fault diagnosis performed by the control device of the fuel cell system of a 5th embodiment. It is a flowchart which shows an example of the control process performed by the control apparatus of the fuel cell system of 6th Embodiment.

Embodiments of the present disclosure will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to those described in the preceding embodiments are given the same reference numerals, and their explanations may be omitted. Further, in the embodiment, when only some of the constituent elements are described, the constituent elements explained in the preceding embodiment can be applied to other parts of the constituent element. The following embodiments can be partially combined with each other, even if not explicitly stated, as long as the combination does not cause any problems.

(First embodiment)
This embodiment will be described with reference to FIGS. 1 and 2. The fuel cell system 1 constitutes a part of a power supply system applied to a home, and is configured to be able to output generated power according to power demand.

As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 10 that outputs electrical energy through an electrochemical reaction between reformed fuel generated in a reformer 34 and an oxidant gas (oxygen in the air in this example). It is equipped with The fuel cell 10 is constituted by a solid oxide fuel cell (ie, SOFC) whose operating temperature is high (eg, 500° C. to 1000° C.). The fuel cell 10 has a stack structure in which a plurality of power generation cells are stacked.

Although not shown, the power generation cell includes a solid oxide electrolyte, an air electrode (ie, cathode), and a fuel electrode (ie, anode). For the fuel electrode, cermet of nickel, which is highly active in shift reactions, etc., and yttria-stabilized zirconia, which is an electrolyte material, is used. The power generation cell of this embodiment uses hydrogen and carbon monoxide produced by reforming raw fuel as reformed fuel. City gas, which is a hydrocarbon-based fuel (that is, gas whose main component is methane), is used as the raw fuel. Note that gas other than city gas may be used as the raw fuel as long as it is a hydrocarbon fuel.

The fuel cell 10 outputs electrical energy through an electrochemical reaction between hydrogen and oxygen shown in reaction formulas F1 and F2 below.

(Fuel electrode) 2H ₂ +2O ^2- → 2H ₂ O+4e ^- … (F1)
(Air electrode) O ₂ +4e ⁻ →2O ²⁻ …(F2)
Further, the fuel cell 10 outputs electrical energy through an electrochemical reaction between carbon monoxide and oxygen shown in reaction formulas F3 and F4 below.

(Fuel electrode) 2CO+2O ^2- →2CO ₂ +4e ^- …(F3)
(Air electrode) O ₂ +4e ⁻ →2O ²⁻ …(F4)
Connected to the fuel cell 10 are a current/voltage detection section 101 that detects current and voltage output from the fuel cell 10, a power conditioner PC for extracting electrical energy generated by the fuel cell 10, and the like.

The power conditioner PC converts DC power generated by the fuel cell 10 into AC power. Specifically, the power conditioner PC includes a DC-DC converter that extracts and boosts the DC power generated by the fuel cell 10, and a DC-AC inverter that converts the DC power into AC power.

A household load is connected to the power conditioner PC via a power line. Thereby, the electrical energy generated by the fuel cell 10 is supplied to the household load via the power conditioner PC.

The fuel cell 10 is arranged inside a heat-insulating housing along with a reformer 34, a combustor 73, etc., which will be described later. The fuel cell 10 is warmed up by the combustor 73. The housing and equipment arranged inside the housing constitute a hot module HM that is maintained at a high temperature in the fuel cell system 1.

The fuel cell 10 has an air path 20 connected to the air inlet side. The air path 20 is provided with a pressure blower 21 that pumps air to the fuel cell 10, an air flow meter 22, an air preheater (not shown), and the like.

The pressure blower 21 is an oxidant gas pump that sucks air from the atmosphere and supplies it to the fuel cell 10. The pressure blower 21 is an electric blower whose operation is controlled by a control signal from a control device 100, which will be described later.

The air flow meter 22 is a device that measures the flow rate of the oxidant gas supplied to the fuel cell 10. The air flow meter 22 is connected to the control device 100 so as to be able to output the detection result of the flow rate of the oxidizing gas to the control device 100, which will be described later.

The air preheater is a heat exchanger that heats the air pumped from the pressure blower 21 by exchanging heat with exhaust gas from the combustor 73, which will be described later. The air preheater is provided to improve the power generation efficiency of the fuel cell 10 by reducing the temperature difference between the air supplied to the fuel cell 10 and the fuel gas.

Further, in the fuel cell 10, a fuel path 30 is connected to the inlet side of the reformed fuel. The fuel path 30 is provided with, in order from the upstream side, a fuel on-off valve 31, a fuel pump 32, a desulfurizer (not shown), a fuel flow meter 33, a reformer 34, and the like.

A portion of the fuel path 30 from the fuel on-off valve 31 to the reformer 34 constitutes a raw fuel path 30A through which the raw fuel flows toward the reformer 34. Further, the portion of the fuel path 30 from the reformer 34 to the fuel cell 10 constitutes a reformed fuel path 30B through which the reformed fuel reformed in the reformer 34 flows to the fuel cell 10.

The fuel on-off valve 31 is a fuel cutoff member that blocks introduction of raw fuel from the outside into the raw fuel path 30A. The fuel on-off valve 31 is provided upstream of the fuel pump 32 in the raw fuel path 30A. More specifically, the fuel on-off valve 31 is provided upstream of a connection point with a circulation path 60, which will be described later, in the raw fuel path 30A. The fuel on-off valve 31 switches between a fuel supply state in which raw fuel can be supplied from the outside and a fuel cutoff state in which raw fuel cannot be supplied from the outside by opening and closing upstream of the fuel pump 32 in the raw fuel path 30A. It is a switching means. The fuel on-off valve 31 is composed of a solenoid valve whose operation is controlled by a control signal from the control device 100.

The fuel pump 32 supplies raw fuel to the reformer 34. The fuel pump 32 is an electric pump whose operation is controlled by a control signal from a control device 100, which will be described later.

Here, a sulfur compound is attached as an odorant to the city gas used as raw fuel, and when the sulfur compound is supplied to the reformer 34 and the fuel cell 10, the reformer 34 and There is a possibility that the catalyst of the fuel cell 10 may be poisoned.

On the other hand, a desulfurizer is provided in the fuel path 30 between the fuel pump 32 and the reformer 34. A desulfurizer removes sulfur contained in raw fuel. The desulfurizer is a hydrodesulfurizer that removes sulfur from the raw fuel by reacting the sulfur contained in the raw fuel with hydrogen. Specifically, the desulfurizer removes sulfur from the raw fuel by reacting the sulfur contained in the raw fuel with hydrogen contained in the reformed fuel from the circulation path 60, which will be described later.

The fuel flow meter 33 is a device that measures the flow rate of raw fuel supplied to the reformer 34. The fuel flow meter 33 is connected to the control device 100 so as to be able to output the detection result of the raw fuel flow rate to the control device 100, which will be described later. In this embodiment, the fuel pump 32 and the fuel flow meter 33 are functional items provided upstream of the reformer 34.

The reformer 34 uses water vapor to reform the raw fuel supplied from the fuel pump 32 to generate reformed fuel. The reformer 34 includes, for example, a steam reforming catalyst containing nickel and a reactor.

Specifically, the reformer 34 heats a mixed gas of raw fuel and water vapor with the heat of the combustor 73, which will be described later, and performs a reforming reaction shown in the following reaction formula F5 and a reforming reaction shown in the reaction formula F6. Generates reformed fuel (hydrogen, carbon monoxide) through a shift reaction.

_CH4 + _H2O →CO+ _H2 ...(F5)
CO+ _H2O → _CO2 + _H2 ...(F6)
The reformed fuel generated in the reformer 34 is supplied to the fuel cell 10 via the reformed fuel path 30B.

Here, the steam reforming in the reformer 34 is an endothermic reaction, and has a characteristic that the reforming rate improves under high temperature conditions. Therefore, the heat of the combustor 73, which will be described later, is transferred to the reformer 34. Specifically, the reformer 34 is configured to be heated by heat exchange with high-temperature exhaust gas discharged from the combustor 73. Further, it is desirable that the reformer 34 be disposed around the fuel cell 10 so that it can absorb heat (radiant heat) released to the surroundings when the fuel cell 10 generates power.

Although not shown, a water supply route is connected to the raw fuel route 30A between the fuel pump 32 and the reformer 34, and the water pump and the reformer 34 supply water from outside the system to this water supply route. A vaporizer is provided to generate water vapor to be supplied to the tank.

An ejector 81 is provided in the fuel path 30 between the fuel pump 32 and the reformer 34 . The ejector 81 uses the raw fuel upstream of the reformer 34 as a driving flow to suck in off-gas fuel flowing through a suction path 82, which will be described later, and supplies it to the reformer 34 together with the raw fuel.

Specifically, the ejector 81 includes a nozzle section 811 that injects fluid, a suction section 812 that sucks fluid from the outlet side of the fuel cell 10, and a fluid that is injected from the nozzle section 811 and a fluid that is sucked from the suction section 812. It has a discharge part 813 that mixes the mixture and discharges it toward the reformer 34.

The nozzle portion 811 has a constriction structure that can eject fluid. The nozzle portion 811 has a fixed aperture structure with a fixed aperture opening. Further, the discharge section 813 has a flow passage cross-sectional area expanding toward the downstream side so that the pressure is increased after the fluid from the nozzle section 811 and the fluid from the suction section 812 are mixed. Note that the nozzle portion 811 may have a variable aperture structure that can change the aperture opening.

The suction section 812 of the ejector 81 is configured to suck fluid from the exit side of the fuel cell 10 using negative pressure on the exit side of the nozzle section 811 . Specifically, a suction path 82 branching from the fuel exhaust path 72 is connected to the suction portion 812 so that fluid flowing through the fuel exhaust path 72, which will be described later, is suctioned.

Further, the fuel path 30 is connected to a circulation path 60 that returns a portion of the reformed fuel flowing through the reformed fuel path 30B to the upstream side of the fuel pump 32 in the raw fuel path 30A as a circulating gas. One end of the circulation path 60 is connected to the reformed fuel path 30B, and the other end is connected between the fuel on-off valve 31 in the raw fuel path 30A and the fuel pump 32, which is a functional item. ing.

A circulation regulating valve 61 is provided in the circulation path 60 . The circulation adjustment valve 61 is a flow rate adjustment member that adjusts the flow rate of the reformed fuel flowing through the circulation path 60. The circulation regulating valve 61 is composed of an electromagnetic valve whose operation is controlled by a control signal from a control device 100, which will be described later.

The circulation path 60 is provided with a circulation temperature sensor 62 that detects the temperature To of the reformed fuel flowing through the circulation path 60. The circulation temperature sensor 62 is provided in a range from the connection point with the reformed fuel path 30B in the circulation path 60 to the circulation adjustment valve 61. Thereby, even when the circulation regulating valve 61 is in the fully closed state, the temperature To of the reformed fuel on the reformed fuel path 30B side in the circulation path 60 can be detected by the circulation temperature sensor 62. Note that the circulation temperature sensor 62 is connected to the control device 100 so as to be able to output the detection result of the temperature To of the reformed fuel to the control device 100, which will be described later.

Here, the ejector 81 has a characteristic that as the mass flow rate of the fluid flowing into the nozzle part 811 as a driving flow increases, the flow rate of the suction fluid sucked from the suction part 812 increases. Therefore, by increasing the mass flow rate of the fluid flowing into the nozzle portion 811 of the ejector 81, it is possible to increase the suction flow rate of off-gas fuel sucked from the suction portion 812.

For example, by opening the circulation regulating valve 61 to increase the circulating gas flowing through the circulation path 60, the driving flow of the ejector 81 can be increased without increasing the amount of fuel supplied from outside the system.

Next, the fuel cell 10 is connected to an off-gas path 70 through which off-gas discharged from the fuel cell 10 flows. The off-gas path 70 includes an air exhaust path 71 through which off-gas air discharged from the fuel cell 10 flows, and a fuel exhaust path 72 through which off-gas fuel exhausted from the fuel cell 10 flows. The air exhaust path 71 is connected to the air outlet side of the fuel cell 10. The fuel discharge path 72 is connected to the fuel outlet side of the fuel cell 10.

A combustor 73 is provided in the off-gas path 70. The combustor 73 generates high-temperature exhaust gas by burning off-gas fuel and off-gas air discharged from the fuel cell 10. Although not shown, the combustor 73 includes a burner for burning fuel. In the combustor 73, combustion of fuel is started by igniting the burner.

An exhaust gas path 74 for discharging high-temperature exhaust gas is connected to the combustor 73. The exhaust gas path 74 is connected to the reformer 34 and the like in order to effectively utilize the heat of the exhaust gas flowing therein. Thereby, the heat of the combustor 73 is transferred to the reformer 34.

Next, the control device 100 that constitutes the electronic control section in the fuel cell system 1 will be explained. The control device 100 is composed of a microcomputer including a processor and memory, and its peripheral circuits. The control device 100 performs various calculations and processes based on a control program stored in a memory, and controls the operation of various control devices connected to the output side.

Various sensors including a current/voltage detection section 101 are connected to the input side of the control device 100, and detection results of the various sensors are input to the control device 100. An operation panel (not shown) is connected to the control device 100. This operation panel is provided with an operation switch for turning on/off power generation of the fuel cell 10, a display for displaying the operating status of the fuel cell 10, and the like.

On the other hand, the output side of the control device 100 is connected to control devices such as a pressure blower 21, a fuel on-off valve 31, a fuel pump 32, a water pump, a circulation adjustment valve 61, and a burner of a combustor 73 (not shown). The operation of these control devices is controlled according to control signals output from the control device 100.

Further, the control device 100 controls the power generated by the fuel cell 10 according to the power demand of the household load, and controls the power conditioner PC accordingly. Note that the power generated by the fuel cell 10 is controlled by controlling the fuel supply system of the fuel cell 10 (that is, the amount of fuel gas supplied to the fuel cell 10).

Further, in parallel with controlling the power generated by the fuel cell 10, the control device 100 controls the power conditioner PC so that the current extracted from the fuel cell 10 (i.e., sweep current) approaches the target current value determined by the target power generation. Control.

Next, the overall operation of the fuel cell system 1 will be briefly explained. In the fuel cell system 1, when the operation switch is turned on, the control device 100 executes a power generation process to cause the fuel cell 10 to output electrical energy. In this power generation process, oxidant gas and reformed fuel are supplied to the fuel cell 10 in amounts suitable for power generation.

Specifically, in the power generation process, raw fuel from outside the system is supplied by the fuel pump 32 to the reformer 34 via the ejector 81, and oxidizing gas is supplied by the pressure blower 21 to the reformer 34 via the air preheater. The fuel is supplied to the fuel cell 10. Additionally, in the power generation process, water pumps supply water to a water evaporator to generate water vapor. This water vapor flows into the reformer 34 together with the raw fuel. In the reformer 34, when a mixed gas of raw fuel and steam is supplied, reformed fuel (hydrogen, carbon monoxide) is generated by a steam reforming reaction. The reformed fuel generated in the reformer 34 then flows into the fuel cell 10.

When supplied with the oxidant gas and reformed fuel, the fuel cell 10 outputs electrical energy through the reactions shown in the above-mentioned reaction formulas F1 to F4. At this time, the fuel cell 10 discharges off-gas fuel and off-gas air. Off-gas fuel and off-gas air are combusted in combustor 73 as combustible gases. The high-temperature exhaust gas generated in the combustor 73 is used as a heating source for the reformer 34 and the like, and then is discharged to the outside of the system as exhaust gas.

As mentioned above, the steam reforming in the reformer 34 is an endothermic reaction, and has the characteristic that the reforming rate improves under high temperature conditions. Therefore, by heating the reformer 34 with the heat of the exhaust gas from the combustor 73, the reforming rate in the reformer 34 can be maintained.

Here, during power generation processing, off-gas fuel containing reformed fuel that has not been consumed by the fuel cell 10 is discharged. A part of this off-gas fuel is reused by being sucked into the ejector 81 via the suction path 82. The flow rate of the off-gas fuel sucked into the ejector 81 (that is, the suction flow rate) depends on the flow rate of the driving flow of the ejector 81. The driving flow of the ejector 81 is adjusted by adjusting the flow rate of the reformed fuel flowing through the circulation path 60 by the circulation adjustment valve 61.

By the way, when the power demand on the load side in the home decreases while the fuel cell 10 is generating power, the surplus power that cannot be consumed on the load side becomes excessive. Therefore, when the power demand on the load side decreases, the control device 100 limits the power generated by the fuel cell 10 using the power conditioner PC.

However, even if the power generated by the fuel cell 10 is limited, unreacted reformed fuel that is not used for power generation increases in the fuel cell 10 due to a delay in response of the fuel supply system to the power limitation. That is, the reformed fuel consumed by the fuel cell 10 decreases, and the hydrogen concentration of the off-gas fuel increases.

In this case, more unreacted gas (for example, hydrogen) than necessary is supplied to the combustor 73, and the temperature of the combustor 73 may rise excessively. When the temperature of the combustor 73 increases excessively, the amount of heating of the reformer 34 by the combustor 73 increases, and the temperature of the reformed fuel produced in the reformer 34 becomes higher than normal. In this case, the high temperature reformed fuel reaches functional components such as the fuel pump 32 via the circulation path 60. This is undesirable because, for example, if the functional product has low heat resistance, it may cause malfunction of the functional product.

In response to this, the control device 100 executes a control process to suppress supply of high temperature reformed fuel to the functional product via the circulation path 60. This control process will be explained with reference to the flowchart shown in FIG. Note that the control process shown in FIG. 2 is executed periodically or irregularly by the control device 100 while the fuel cell 10 is generating power.

As shown in FIG. 2, in step S100, the control device 100 reads signals from various sensors, an operation panel, a power conditioner PC, etc. connected to the input side.

Subsequently, the control device 100 determines whether a temperature abnormality has occurred in the reformed fuel returned from the circulation path 60 to the raw fuel path 30A. Specifically, in step S110, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth. That is, the control device 100 determines whether the temperature detected by the circulation temperature sensor 62 exceeds the predetermined temperature Tth. The predetermined temperature Tth is set, for example, within a temperature range that is below the normal operating temperature of the reformer 34 (for example, 400° C.) and above the heat-resistant temperature of functional components such as the fuel pump 32.

As a result of the determination process in step S110, if the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 returns to step S100. On the other hand, if the temperature To of the reformed fuel exceeds the predetermined temperature Tth, in step S120, the control device 100 adjusts the circulation so as to reduce the flow rate of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A. Control valve 61. Specifically, when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth, the control device 100 controls the circulation adjustment valve 61 to be fully closed. As a result, high-temperature reformed fuel no longer flows to the raw fuel path 30A via the circulation path 60, so that functional components such as the fuel pump 32 can be thermally protected.

Subsequently, in step S130, the control device 100 executes a temperature lowering process to lower the temperature of the reformed fuel passing through the circulation path 60. The control device 100 of this embodiment controls the fuel pump 32 so that the amount of raw fuel supplied to the reformer 34 is reduced as a temperature reduction process, and also controls the oxidant gas supplied to the fuel cell 10. The pressure blower 21 is controlled so that the amount of supply increases.

Here, if the amount of raw fuel supplied to the reformer 34 is excessively reduced, the fuel cell 10 will run out of fuel. If the fuel cell 10 continues to run out of fuel, deterioration of the catalyst used inside the fuel cell 10 will be accelerated, which is undesirable.

Therefore, the control device 100 of the present embodiment controls the fuel pump 32 so that the amount of raw fuel supplied to the reformer 34 is reduced to an amount corresponding to the power demand on the load side. According to this, by reducing the amount of reformed fuel supplied to the fuel cell 10, the amount of unreacted hydrogen in the fuel cell 10 is reduced. As a result, an increase in the hydrogen concentration of the off-gas fuel supplied to the combustor 73 is suppressed, and the temperature of the combustor 73 is reduced. When the temperature of the combustor 73 decreases, the amount of heating of the reformer 34 by the combustor 73 decreases, so that the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A decreases.

Further, the control device 100 controls the pressure blower 21 so that the amount of oxidant gas supplied to the fuel cell 10 increases more than the amount corresponding to the power demand on the load side. According to this, a large flow rate of the oxidant gas passes through the air preheater, thereby reducing the temperature difference between the oxidant gas before and after the air preheater, and low-temperature oxidant gas is supplied to the fuel cell 10. When the low-temperature oxidant gas is supplied to the fuel cell 10, the temperature of the off-gas air discharged from the fuel cell 10 decreases. Then, the low-temperature off-gas air discharged from the fuel cell 10 flows into the combustor 73, thereby reducing the temperature of the combustor 73.

Subsequently, in step S140, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A is equal to or lower than a predetermined temperature Tth. Note that the process in step S140 is executed after a predetermined period of time has elapsed since the control device 100 executed the process in step S130. This predetermined time is set, for example, to the time required from executing the process of step S130 until the hydrogen concentration of the off-gas fuel flowing into the combustor 73 starts to decrease.

If the result of the determination process in step S140 is that the temperature To of the reformed fuel still exceeds the predetermined temperature Tth, the temperature reduction process in step S130 will not function effectively. The reason why the temperature reduction process does not function effectively is, for example, failure of the fuel pump 32 or the pressure blower 21. If the temperature reduction process does not function effectively, the failed equipment will need to be repaired. Therefore, if the temperature To of the reformed fuel exceeds the predetermined temperature Tth, the control device 100 stops the system in step S150.

Specifically, the control device 100 controls the circulation adjustment valve 61 so that the circulation path 60 is fully closed, stops each of the fuel pump 32 and the pressure blower 21, and also stops the supply of fuel to the raw fuel path 30A. The fuel on-off valve 31 is controlled so that the introduction of raw fuel is blocked.

According to this, the circulation path 60 is completely closed by the circulation adjustment valve 61, and high temperature reformed fuel no longer flows from the circulation path 60 to the raw fuel path 30A, so that functional components such as the fuel pump 32 can be thermally protected. I can do it.

Further, by stopping each of the fuel pump 32 and the pressure blower 21 and completely closing the raw fuel path 30A by the fuel on-off valve 31, it is possible to stop power generation in the fuel cell 10 and cause the combustor 73 to misfire. .

On the other hand, if the result of the determination process in step S140 is that the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, this is a situation in which the temperature reduction process in step S130 effectively functions, and the temperature To of the reformed fuel is again set to the predetermined temperature Tth. Even if the temperature exceeds Tth, it can be coped with. Therefore, when the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 controls the circulation regulating valve 61 in step S160 so that the circulation path 60 is fully open, and returns to step S100. return. Note that when returning to step S100, the control device 100 returns the fuel pump 32 and the pressure blower 21 to the state before the temperature reduction process.

In the fuel cell system 1 described above, when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth, the control device 100 adjusts the circulation so that the circulation path 60 is completely closed. Control valve 61.

According to this, supply of high temperature reformed fuel to functional items such as the fuel pump 32 via the circulation path 60 is suppressed. Therefore, it is possible to suppress the occurrence of malfunction of the functional product due to supply of high-temperature reformed fuel to the functional product. Furthermore, it becomes possible to use inexpensive functional items such as the fuel pump 32 that have low heat resistance.

Additionally, when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth, the control device 100 executes a temperature reduction process to reduce the temperature of the combustor 73. Specifically, when the temperature To of the reformed fuel exceeds a predetermined temperature Tth, the control device 100 controls the fuel pump 32 so that the amount of raw fuel supplied to the reformer 34 decreases, and also controls the fuel cell The pressure blower 21 is controlled so that the amount of oxidizing gas supplied to the oxidant gas 10 is increased.

According to this, even if the temperature To of the reformed fuel returned from the circulation route 60 to the raw fuel route 30A exceeds the predetermined temperature Tth, the temperature To of the reformed fuel returned from the circulation route 60 to the raw fuel route 30A can be lowered. Thus, the power generation state of the fuel cell 10 can be continued. That is, the fuel cell system 1 can maintain the power generation state of the fuel cell 10 while suppressing the occurrence of malfunctions of the functional products due to the supply of high-temperature reformed fuel to the functional products.

Further, when the temperature To of the reformed fuel becomes normal after executing the temperature reduction process, the control device 100 returns the opening degree of the circulation regulating valve 61 to the original full open position. According to this, the fuel cell 10 can be returned to an efficient power generation state without stopping the system.

(Modified example of the first embodiment)
In the first embodiment described above, as a temperature reduction process to reduce the temperature of the combustor 73, the amount of raw fuel supplied to the reformer 34 is decreased, and the amount of oxidant gas supplied to the fuel cell 10 is increased. However, the temperature lowering treatment is not limited to this. The temperature lowering process may be, for example, a process of decreasing the amount of raw fuel supplied to the reformer 34 or increasing the amount of oxidant gas supplied to the fuel cell 10. Further, the temperature reduction process is, for example, a process of increasing the supply amount of oxidant gas when the temperature of the combustor 73 cannot be sufficiently lowered even if the supply amount of raw fuel to the reformer 34 is reduced. It may be . These also apply to subsequent embodiments.

In the first embodiment described above, the temperature serving as the determination criterion in step S140 is the same as the predetermined temperature Tth serving as the determination criterion in step S110, but is not limited to this, for example, it may be lower than the predetermined temperature Tth. It may be the same temperature.

(Second embodiment)
Next, a second embodiment will be described with reference to FIGS. 3 to 5. In this embodiment, parts that are different from the first embodiment will be mainly explained.

As shown in FIG. 3, the fuel cell system 1 includes a heat exchange device 63 that radiates heat from the reformed fuel flowing through the circulation path 60. This heat exchange device 63 is a device for suppressing high temperature reformed fuel from being supplied to functional products via the circulation path 60.

The heat exchange device 63 is configured to radiate heat from the reformed fuel flowing through the circulation path 60 when the fuel cell 10 generates electricity. Specifically, the heat exchange device 63 includes a radiator 631 through which the reformed fuel passes, and a blower 632 that supplies outside air to exchange heat with the reformed fuel flowing through the radiator 631.

The radiator 631 is a heat exchanger that radiates heat from the reformed fuel flowing through the circulation path 60 by exchanging heat with outside air. As the heat radiator 631, for example, a fin-and-tube type heat exchanger can be adopted. The heat radiator 631 is arranged upstream of the circulation temperature sensor 62 in the circulation path 60. Thereby, the circulation temperature sensor 62 detects the temperature of the reformed fuel after the heat is radiated by the radiator 631.

The blower 632 includes an electric blower having a cooling fan and an electric motor that rotates the cooling fan. The operation of the blower 632 is controlled according to a control signal from the control device 100. Further, the blower 632 is configured to be able to output information indicating the operating state (for example, rotation speed) of the cooling fan to the control device 100 as diagnostic information.

Here, if the heat exchange device 63 does not operate normally due to a failure of the blower 632, the reformed fuel is supplied to the functional products via the circulation path 60 at a higher temperature than when the heat exchange device 63 operates normally. It will be done.

In response to this, the control device 100 executes a control process to suppress supply of high temperature reformed fuel to the functional product via the circulation path 60. This control process will be explained with reference to the flowchart shown in FIG. The flowchart shown in FIG. 4 corresponds to the flowchart shown in FIG. Steps S200 to S220 shown in FIG. 4 are substantially the same as steps S100 to S120 shown in FIG. 2. Therefore, in this embodiment, a detailed explanation of the same processing contents as in the first embodiment will be omitted.

As shown in FIG. 4, in step S200, the control device 100 reads signals from various sensors connected to the input side. Subsequently, in step S210, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth. Note that the predetermined temperature Tth is, for example, within a temperature range that includes the temperature To of the reformed fuel after passing through the radiator 631 (for example, To±50°C) when the heat exchange device 63 is operating normally. Set.

As a result of the determination process in step S210, if the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 returns to step S200. On the other hand, if the temperature To of the reformed fuel exceeds the predetermined temperature Tth, the control device 100 controls the circulation regulating valve 61 to be fully closed in step S220.

Subsequently, the control device 100 performs a failure diagnosis of the heat exchange device 63 in step S230. In this failure diagnosis, it is determined whether the heat exchange device 63 is operating normally. Details of the failure diagnosis will be explained with reference to the flowchart shown in FIG.

As shown in FIG. 5, the control device 100 reads various signals including diagnostic information of the blower 632 in step S231. In step S232, the control device 100 determines whether the rotation speed of the cooling fan of the blower 632 is abnormal based on the diagnostic information. For example, the control device 100 determines that there is an abnormality when the rotation speed of the cooling fan deviates from the target rotation speed by 10% or more.

If the rotation speed of the cooling fan is not abnormal as a result of the determination process in step S232, the control device 100 sets the failure determination flag to "off" indicating "no device abnormality" in step S233, and exits the process.

On the other hand, if the rotation speed of the cooling fan is abnormal as a result of the determination process in step S232, the control device 100 sets the failure determination flag to "ON" indicating "device abnormality" in step S234, and performs processing. Go through.

Returning to FIG. 4, after performing the failure diagnosis, the control device 100 determines in step S240 whether there is an "equipment failure". The determination in step S240 is made based on the failure determination flag.

If the result of the determination process in step S240 is "no equipment failure", the reason why the temperature To of the reformed fuel passing through the circulation path 60 exceeds the predetermined temperature Tth is due to a change in the power demand on the load side, etc. There is a high possibility that this is a transient event. Therefore, in step S250, the control device 100 executes a temperature reduction process to reduce the temperature of the reformed fuel passing through the circulation path 60. The determination process in step S250 is similar to the process in step S130 in FIG. 2, so the description thereof will be omitted.

Subsequently, in step S260, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A is equal to or lower than a predetermined temperature Tth. If the result of the determination process in step S260 is that the temperature To of the reformed fuel exceeds the predetermined temperature Tth, the control device 100 returns to step S250 and continues the temperature reduction process. On the other hand, if the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 controls the circulation regulating valve 61 so that the circulation path 60 is fully open in step S270, and returns to step S200. . Note that when returning to step S200, the control device 100 returns the fuel pump 32 and the pressure blower 21 to the state before the temperature reduction process.

Further, if the result of the determination process in step S240 is "equipment failure", the temperature To of the reformed fuel passing through the circulation path 60 exceeds the predetermined temperature Tth because the heat exchange device 63 does not operate normally. This is likely to be the cause. In this case, it is necessary to repair the heat exchange device 63. Therefore, control device 100 stops the system in step S280. The determination process in step S280 is similar to the process in step S150 in FIG. 2, so its description will be omitted.

The fuel cell system 1 described above includes the same configuration and common operations as the first embodiment. Therefore, the fuel cell system 1 can obtain the same effects as the first embodiment from the common configuration and common operation.

In addition, the fuel cell system 1 determines whether or not the heat exchange device 63 operates normally, and changes the subsequent treatment depending on the result. Specifically, in this embodiment, in a situation where the heat exchange device 63 does not operate normally, the fuel pump 32 and the pressure blower 21 are stopped, the raw fuel path 30A is shut off by the fuel on-off valve 31, and further, The circulation path 60 is shut off by the circulation regulating valve 61. According to this, it is possible to avoid problems caused by the heat exchange device 63 not operating normally.

On the other hand, under a situation where the heat exchange device 63 is operating normally, the temperature To of the reformed fuel passing through the circulation path 60 is lowered by executing the temperature lowering process. Then, after the temperature To of the reformed fuel becomes normal, the opening degree of the circulation regulating valve 61 is returned to the original full open position, thereby returning the fuel cell 10 to an efficient power generation state without stopping the system. be able to.

Further, the temperature lowering process lowers the temperature To of the reformed fuel passing through the circulation path 60 by changing the amount of raw fuel supplied by the fuel pump 32 and the amount of oxidant gas supplied by the pressure blower 21. According to this, in order to lower the temperature To of the reformed fuel passing through the circulation path 60, it is not necessary to increase the capacity of the radiator 631 of the heat exchange device 63 or to increase the output of the blower 632.

(Modified example of second embodiment)
In the second embodiment described above, the temperature serving as the determination criterion in step S260 is the same as the predetermined temperature Tth serving as the determination criterion in step S210, but is not limited to this, for example, it may be lower than the predetermined temperature Tth. It may be the same temperature. This also applies to subsequent embodiments.

In the second embodiment described above, it has been explained that the temperature reduction process is the same as the process in step S130 in FIG. may be included.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. 6 and 7. In this embodiment, parts that are different from the second embodiment will be mainly described.

As shown in FIG. 6, a reforming temperature sensor 35 that detects the temperature of the reformer 34 is added to the fuel cell system 1 of this embodiment. The reforming temperature sensor 35 detects the temperature of the reformed fuel flowing out from the reformer 34 as the reforming temperature Tr. Note that the reforming temperature sensor 35 is connected to the control device 100 so as to be able to output the detection result of the temperature of the reformer 34 to the control device 100, which will be described later.

The other configurations are the same as in the second embodiment. Hereinafter, the failure diagnosis executed by the control device 100 of this embodiment will be explained with reference to the flowchart shown in FIG. 7. The flowchart shown in FIG. 7 corresponds to the flowchart shown in FIG.

As shown in FIG. 7, the control device 100 reads various signals including the detection results of the circulation temperature sensor 62 and the reforming temperature sensor 35 in step S231A.

Subsequently, in step S232A, the control device 100 determines that the temperature difference (=Tr - To) between the temperature To of the reformed fuel after passing through the radiator 631 and the reforming temperature Tr exceeds a predetermined determination reference value ΔTroth. Determine whether it exceeds the limit. The predetermined determination reference value ΔTroth is set based on the temperature difference before and after the radiator 631 that is assumed in normal times and the heat loss from the reformer 34 to the radiator 631 in the circulation path 60.

As a result of the determination process in step S232A, if the temperature difference between the reformed fuel temperature To and the reforming temperature Tr exceeds the predetermined determination reference value ΔTroth, the reformed fuel temperature To is lower than the reforming temperature Tr. Since the temperature has decreased sufficiently, it is considered that the heat exchange device 63 is operating normally. Therefore, if the temperature difference between the reformed fuel temperature To and the reforming temperature Tr exceeds the predetermined determination reference value ΔTroth, the control device 100 sets the failure determination flag to "no equipment abnormality" in step S233A. Set it to "off" to exit the process.

On the other hand, if the temperature difference between the reformed fuel temperature To and the reforming temperature Tr is less than the predetermined judgment reference value ΔTroth, it means that the reformed fuel temperature To has not decreased sufficiently compared to the reforming temperature Tr. , it is considered that the heat exchange device 63 is not operating normally. Therefore, if the temperature difference between the reformed fuel temperature To and the reforming temperature Tr is less than or equal to the predetermined determination reference value ΔTroth, the control device 100 sets the failure determination flag to "equipment abnormality" in step S234A. Set it to "on" and exit the process.

Other operations are similar to those in the second embodiment. The fuel cell system 1 of this embodiment includes the same configuration and common operations as the second embodiment. Therefore, the fuel cell system 1 can obtain the same effects as the second embodiment from the common configuration, common operation, and the like.

In particular, the fuel cell system 1 of the present embodiment diagnoses the failure of the heat exchange device 63 based on the temperature To of the reformed fuel after passing through the radiator 631 and the reforming temperature Tr. Therefore, for example, even if the heat exchange device 63 has a structure that cannot output diagnostic information, it is possible to diagnose the failure of the heat exchange device 63.

(Modification of third embodiment)
In the third embodiment described above, the failure diagnosis of the heat exchange device 63 is performed based on the temperature difference of the reformed fuel before and after the radiator 631, but the failure diagnosis is not limited to this. The failure diagnosis may be performed based on, for example, diagnostic information of the blower 632 and the temperature difference of the reformed fuel before and after the radiator 631. This also applies to subsequent embodiments.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS. 8 and 9. In this embodiment, parts that are different from the second embodiment will be mainly described.

As shown in FIG. 8, the fuel cell system 1 includes an inlet temperature sensor 62A that detects the temperature Ti of the reformed fuel flowing into the radiator 631, and an inlet temperature sensor 62A that detects the temperature Ti of the reformed fuel flowing into the radiator 631 with respect to the circulation path 60. An outlet temperature sensor 62B is provided to detect the temperature To. The inlet temperature sensor 62A and the outlet temperature sensor 62B are each connected to the control device 100 so as to be able to output the detection result of the temperature of the reformed fuel to the control device 100, which will be described later.

The other configurations are the same as in the second embodiment. Hereinafter, the failure diagnosis executed by the control device 100 of this embodiment will be explained with reference to the flowchart shown in FIG. 9. The flowchart shown in FIG. 9 corresponds to the flowchart shown in FIG.

As shown in FIG. 9, in step S231B, the control device 100 reads various signals including the detection result of the inlet temperature sensor 62A and the detection result of the outlet temperature sensor 62B.

Subsequently, in step S232B, the control device 100 determines the temperature difference (=Ti- To) exceeds a predetermined determination reference value ΔTioth. The predetermined determination reference value ΔTioth is set based on the temperature difference before and after the radiator 631 that is assumed in normal times.

As a result of the determination process in step S232B, if the temperature difference of the reformed fuel before and after the radiator 631 exceeds the predetermined determination reference value ΔTioth, the temperature of the reformed fuel has been sufficiently reduced by the radiator 631. , it is considered that the heat exchange device 63 is operating normally. Therefore, if the temperature difference of the reformed fuel before and after the radiator 631 exceeds the predetermined determination reference value ΔTioth, the control device 100 changes the failure determination flag to "No Equipment Abnormality" in step S233B. "Off" and exit the process.

On the other hand, if the temperature difference of the reformed fuel before and after the radiator 631 is less than the predetermined judgment reference value ΔTioth, the temperature of the reformed fuel has not been sufficiently lowered by the radiator 631, and the heat exchange device 63 is operating normally. It is thought that it is not working. Therefore, if the temperature difference of the reformed fuel before and after the radiator 631 is equal to or less than the predetermined determination reference value ΔTioth, the control device 100 sets the failure determination flag to "on" indicating "equipment abnormality" in step S234B. ” and exit the process.

Other operations are similar to those in the second embodiment. The fuel cell system 1 of this embodiment includes the same configuration and common operations as the second embodiment. Therefore, the fuel cell system 1 can obtain the same effects as the second embodiment from the common configuration, common operation, and the like.

In particular, the fuel cell system 1 of this embodiment performs failure diagnosis of the heat exchange device 63 based on the temperature difference of the reformed fuel before and after the radiator 631. Therefore, for example, even if the heat exchange device 63 has a structure that cannot output diagnostic information, it is possible to diagnose the failure of the heat exchange device 63.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIG. 10. In this embodiment, parts that are different from the second embodiment will be mainly explained. The fuel cell system 1 of this embodiment is different from the second embodiment in the fault diagnosis executed by the control device 100.

Hereinafter, the failure diagnosis executed by the control device 100 of this embodiment will be explained with reference to the flowchart shown in FIG. 10. The flowchart shown in FIG. 10 corresponds to the flowchart shown in FIG.

As shown in FIG. 10, the control device 100 reads various signals including the detection results of the current/voltage detection section 101 in step S231C.

Subsequently, in step S232C, the control device 100 determines whether the power generation output of the fuel cell 10 fluctuates before and after the temperature abnormality of the reformed fuel occurs. Specifically, the control device 100 calculates the fluctuation value of the power generation output of the fuel cell 10 before and after the temperature abnormality of the reformed fuel occurs based on the detection result of the current/voltage detection unit 101, and calculates the fluctuation value of the power generation output of the fuel cell 10. is within a predetermined value. Note that the predetermined value is set based on a fluctuation value of the power generation output that is assumed to cause a temperature abnormality.

As a result of the determination process in step S232C, if the power generation output of the fuel cell 10 fluctuates before and after the temperature abnormality of the reformed fuel occurs, the temperature abnormality is not due to a failure of the heat exchange device 63, but the power generation output of the fuel cell 10. This is thought to be due to fluctuations. Therefore, if the power generation output of the fuel cell 10 fluctuates before and after the temperature abnormality, the control device 100 sets the failure determination flag to "off" indicating "no device abnormality" in step S233C, and performs processing. Go through.

On the other hand, if the power generation output of the fuel cell 10 does not fluctuate before and after the temperature abnormality of the reformed fuel occurs, it is considered that the temperature abnormality is caused by a failure of the heat exchange device 63. Therefore, if the power generation output of the fuel cell 10 does not fluctuate before and after the temperature abnormality, the control device 100 sets the failure determination flag to "on" indicating "equipment abnormality" in step S234C, and performs processing. Go through.

Other operations are similar to those in the second embodiment. The fuel cell system 1 of this embodiment includes the same configuration and common operations as the second embodiment. Therefore, the fuel cell system 1 can obtain the same effects as the second embodiment from the common configuration, common operation, and the like.

In particular, the fuel cell system 1 of the present embodiment diagnoses the failure of the heat exchange device 63 based on whether the power generation output of the fuel cell 10 fluctuates before and after the temperature abnormality that causes the reformed fuel temperature abnormality. . Therefore, for example, even if the heat exchange device 63 has a structure that cannot output diagnostic information, it is possible to diagnose the failure of the heat exchange device 63.

(Modification of fifth embodiment)
In the fifth embodiment described above, the failure diagnosis of the heat exchange device 63 is performed based on whether or not the power generation output of the fuel cell 10 fluctuates before and after a temperature abnormality. Not limited. The failure diagnosis may be performed based on, for example, diagnostic information of the blower 632 and the power generation output of the fuel cell 10 before and after the temperature abnormality.

In the fifth embodiment described above, the failure diagnosis of the heat exchange device 63 is performed based on whether or not the power generation output of the fuel cell 10 fluctuates before and after the temperature abnormality of the reformed fuel occurs. but not limited to. For example, the failure diagnosis of the heat exchange device 63 may be performed based on whether the current taken out from the fuel cell 10 (that is, the sweep current) is fluctuating.

(Sixth embodiment)
Next, a sixth embodiment will be described with reference to FIG. 11. In this embodiment, parts that are different from the first embodiment will be mainly explained.

The fuel cell system 1 of this embodiment differs from the first embodiment in the way to deal with a case where a temperature abnormality occurs in the reformed fuel. The control processing executed by the control device 100 of this embodiment will be described below with reference to the flowchart shown in FIG. 11. The flowchart shown in FIG. 11 corresponds to the flowchart shown in FIG. Step S300, step S310, and step S330 to step S360 shown in FIG. 11 are substantially the same as step S100, step S110, and step S130 to step S160 shown in FIG. Therefore, in this embodiment, a detailed explanation of the same processing contents as in the first embodiment will be omitted.

As shown in FIG. 11, in step S300, the control device 100 reads signals from various sensors connected to the input side. Then, in step S310, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth.

As a result of the determination process in step S310, if the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 returns to step S300. On the other hand, if the temperature To of the reformed fuel exceeds the predetermined temperature Tth, in step S320, the control device 100 adjusts the circulation so as to reduce the flow rate of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A. Control valve 61.

Specifically, when the temperature To of the reformed fuel exceeds the predetermined temperature Tth, the control device 100 controls the circulation regulating valve 61 not to be fully open but to be slightly opened. The micro-opening state is such that the flow rate of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A is set to a level that hardly affects the heat resistance of the functional product.

Subsequently, in step S330, the control device 100 executes a temperature reduction process to reduce the temperature of the reformed fuel passing through the circulation path 60. Then, in step S340, the control device 100 determines whether the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A is equal to or lower than a predetermined temperature Tth. As a result, if the temperature To of the reformed fuel exceeds the predetermined temperature Tth, the control device 100 stops the system in step S350. On the other hand, if the temperature To of the reformed fuel is equal to or lower than the predetermined temperature Tth, the control device 100 controls the circulation regulating valve 61 so that the circulation path 60 is fully open in step S360, and returns to step S300. .

The fuel cell system 1 described above includes the same configuration and common operations as the first embodiment. Therefore, the fuel cell system 1 can obtain the same effects as the first embodiment from the common configuration and common operation.

In particular, in the fuel cell system 1 of the present embodiment, when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth, the circulation regulating valve 61 is set to a minute opening by the control device 100. It is controlled to the state that becomes.

According to this, the flow rate of the high temperature reformed fuel flowing from the circulation path 60 to the raw fuel path 30A is restricted, so that functional components such as the fuel pump 32 can be thermally protected. Furthermore, since the supply of reformed fuel from the circulation path 60 to the raw fuel path 30A continues, albeit slightly, the power generation efficiency of the fuel cell 10 can be improved and the supply of hydrogen to the hydrodesulfurizer can be continued. I can do it.

(Modified example of the sixth embodiment)
The solution to the case where temperature abnormality occurs in the reformed fuel described in the sixth embodiment is a system configuration other than the system configuration shown in the first embodiment (for example, the system configuration shown in the second embodiment). It is also applicable to

(Other embodiments)
Although typical embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be modified in various ways, for example, as described below.

In the above embodiment, a hydrodesulfurizer is used as an example of the desulfurizer, but the desulfurizer is not limited to this, and the desulfurizer may be configured with something other than the hydrodesulfurizer.

In the above embodiment, the air flow meter 22 and the fuel flow meter 33 are provided, but the fuel cell system 1 is not limited to this. You don't have to.

In the above-described embodiment, the example is shown in which the heat of exhaust gas from the combustor 73 is transferred to the reformer 34, but the reformer 34 is not limited to this. may be placed close to the combustor 73 so that the

In the above-described embodiment, an air-cooled device that cools the reformed fuel with outside air is exemplified as the heat exchange device 63, but the heat exchange device 63 is not limited to this. It may be configured with a liquid-cooled device for cooling.

In the above-described embodiment, the ejector 81 is provided in the fuel path 30, but the present invention is not limited to this, and the fuel cell system 1 may not be provided with the ejector 81.

In the above-described embodiment, it is determined whether the temperature To of the reformed fuel returned to the raw fuel path 30A exceeds the predetermined temperature Tth based on the detected value of the circulation temperature sensor 62. The determination of whether or not the temperature is high is not limited to this. The determination as to whether the reformed fuel is at a high temperature may be performed based on a physical quantity (for example, the pressure of the reformed fuel) that has a correlation with the temperature To of the reformed fuel.

As in the above-described embodiment, it is desirable to perform the temperature reduction process when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds the predetermined temperature Tth, but the fuel cell system 1 is limited to this. Not done. For example, when the temperature To of the reformed fuel returned from the circulation path 60 to the raw fuel path 30A exceeds a predetermined temperature Tth, the fuel cell system 1 does not perform the temperature reduction process or performs the system operation instead of the temperature reduction process. It may also be possible to perform processing to stop the.

Although, as in the above-described embodiment, the system is immediately stopped when the heat exchange device 63 does not operate normally, the fuel cell system 1 is not limited to this. For example, when the heat exchange device 63 does not operate normally, the fuel cell system 1 executes a temperature reduction process or a notification process to notify the outside of the abnormality of the heat exchange device 63. Good too.

In the above-described embodiment, the fuel pump 32 and the fuel flow meter 33 are exemplified as functional items provided upstream of the reformer 34 in the raw fuel path 30A, but the functional items are not limited thereto. Items other than the fuel flow meter 33 may be included. Although the example in which the fuel cell 10 is constituted by a solid oxide fuel cell is illustrated, the fuel cell 10 is not limited to this, and may be constituted by, for example, a solid polymer type fuel cell (i.e., PEFC). It's okay.

In the above-described embodiment, the fuel cell 10 is configured as a solid oxide fuel cell, but the fuel cell 10 is not limited to this, and the fuel cell 10 may be, for example, a solid polymer type fuel cell (i.e., PEFC).

In the above-described embodiment, the fuel cell system 1 is applied to a household power supply system, but the fuel cell system 1 is not limited to this, and can also be applied to, for example, a commercial facility or factory power supply system. be.

In the embodiments described above, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is specifically specified that they are essential, or where they are clearly considered essential in principle.

In the embodiments described above, when numerical values such as the number, numerical value, amount, range, etc. of the constituent elements of the embodiment are mentioned, it is especially specified that it is essential, or it is clearly limited to a specific number in principle. It is not limited to that specific number, except in certain cases.

In the above-described embodiments, when referring to the shape, positional relationship, etc. of components, etc., we refer to the shape, positional relationship, etc., unless explicitly stated or in principle limited to a specific shape, positional relationship, etc. etc., but not limited to.

The control unit and the method described in the present disclosure are implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. may be done. The controller and techniques described in this disclosure may be implemented by a dedicated computer provided by a processor configured with one or more dedicated hardware logic circuits. The control unit and its method described in the present disclosure are configured by a combination of a processor and memory programmed to execute one or more functions, and a processor configured with one or more hardware logic circuits. It may also be implemented on one or more dedicated computers. The computer program may also be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

(summary)
According to the first aspect shown in some or all of the embodiments described above, in the fuel cell system, when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature, The flow rate adjustment member is controlled to throttle the flow rate of reformed fuel returned from the circulation path to the raw fuel path.

According to the second aspect, when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature, the control device performs reforming so that the amount of raw fuel supplied to the reformer is reduced. Controls the fuel pump that supplies raw fuel to the fuel tank.

According to this, when the temperature of reformed fuel exceeds a predetermined temperature, the amount of raw fuel supplied to the reformer decreases, and the amount of reformed fuel supplied to the fuel cell decreases, so the amount of reformed fuel supplied to the combustor decreases. This suppresses the increase in the hydrogen concentration of the off-gas fuel. When the increase in the hydrogen concentration of the off-gas fuel is suppressed, the temperature of the combustor decreases and the amount of heating of the reformer by the combustor decreases, which reduces the temperature of the reformed fuel returned from the circulation path to the raw fuel path. can be lowered. In this case, while maintaining the power generation state of the fuel cell, it is possible to suppress the occurrence of malfunction of the functional product due to the supply of high-temperature reformed fuel to the functional product.

According to the third aspect, the control device controls the fuel so that when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature, the amount of oxidant gas supplied to the fuel cell increases. Controls the oxidant gas pump that supplies oxidant gas to the battery.

The oxidant gas does not pass through the reformer and tends to be at a lower temperature than the reformed fuel. Therefore, when the temperature of the reformed fuel exceeds a predetermined temperature, if the amount of oxidant gas supplied to the fuel cell is increased, low-temperature off-gas air from the fuel cell will flow into the combustor. temperature can be lowered. As a result, the amount of heating of the reformer by the combustor is reduced, so that the temperature of the reformed fuel returned from the circulation path to the raw fuel path can be lowered. In this case, while maintaining the power generation state of the fuel cell, it is possible to suppress the occurrence of malfunction of the functional product due to the supply of high-temperature reformed fuel to the functional product.

According to the fourth aspect, the fuel cell system includes a heat exchange device that radiates heat from the reformed fuel flowing through the circulation path. The raw fuel route is provided with a fuel cutoff member that blocks introduction of raw fuel from the outside into the raw fuel route upstream of the connection point with the circulation route.

If the heat exchange device does not operate normally when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature, the control device controls the flow rate adjustment member so that the circulation path is fully closed. do. In addition, the control device stops each of the fuel pump that supplies raw fuel to the reformer and the oxidizing gas pump that supplies oxidizing gas to the fuel cell, and the introduction of raw fuel to the raw fuel path is cut off. The fuel cutoff member is controlled as follows.

According to this, when the heat exchange device does not operate normally, the temperature of the reformed fuel returned from the circulation path to the raw fuel path tends to become constantly high. Therefore, in situations where the heat exchange device does not operate normally, the fuel pump and oxidizer gas pump are stopped, the raw fuel path is shut off by the fuel shutoff member, and the circulation path is shut off by the flow rate adjustment member. It is desirable to shut down the fuel cell system.

10 Fuel cell 30A Raw fuel route 30B Reformed fuel route 32 Fuel pump (part of functional products)
34 Reformer 60 Circulation path 61 Circulation adjustment valve (flow rate adjustment member)
73 Combustor 100 Control device

Claims (3)

A fuel cell system,
a reformer (34) that generates reformed fuel by reforming raw fuel input from the outside;
a fuel cell (10) that outputs electrical energy through an electrochemical reaction between the reformed fuel generated in the reformer and the oxidizing gas;
a combustor (73) that burns off-gas fuel and off-gas air discharged from the fuel cell;
a raw fuel path (30A) for flowing raw fuel toward the reformer;
functional products (32, 33) provided upstream of the reformer in the raw fuel route;
a reformed fuel path (30B) for flowing the reformed fuel generated in the reformer to the fuel cell;
a circulation path (60) that returns a portion of the reformed fuel flowing through the reformed fuel path upstream of the functional product in the raw fuel path;
a flow rate adjustment member (61) that adjusts the flow rate of the reformed fuel flowing through the circulation path;
A control device (100) that controls the flow rate adjustment member,
The reformer is configured to receive heat from the combustor, and
The control device controls the flow rate adjustment member to throttle the flow rate of the reformed fuel returned from the circulation path to the raw fuel path when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. A fuel cell system that controls a fuel pump (32) that supplies raw fuel to the reformer so that the amount of raw fuel supplied to the reformer is reduced. A fuel cell system,
a reformer (34) that generates reformed fuel by reforming raw fuel input from the outside;
a fuel cell (10) that outputs electrical energy through an electrochemical reaction between the reformed fuel generated in the reformer and the oxidizing gas;
a combustor (73) that burns off-gas fuel and off-gas air discharged from the fuel cell;
a raw fuel path (30A) for flowing raw fuel toward the reformer;
functional products (32, 33) provided upstream of the reformer in the raw fuel route;
a reformed fuel path (30B) for flowing the reformed fuel generated in the reformer to the fuel cell;
a circulation path (60) that returns a portion of the reformed fuel flowing through the reformed fuel path upstream of the functional product in the raw fuel path;
a flow rate adjustment member (61) that adjusts the flow rate of the reformed fuel flowing through the circulation path;
A control device (100) that controls the flow rate adjustment member,
The reformer is configured to receive heat from the combustor, and
The control device controls the flow rate adjustment member to throttle the flow rate of the reformed fuel returned from the circulation path to the raw fuel path when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. and controlling an oxidizing gas pump (21) that supplies oxidizing gas to the fuel cell so that the amount of oxidizing gas supplied to the fuel cell increases. A fuel cell system,
a reformer (34) that generates reformed fuel by reforming raw fuel input from the outside;
a fuel cell (10) that outputs electrical energy through an electrochemical reaction between the reformed fuel generated in the reformer and the oxidizing gas;
a combustor (73) that burns off-gas fuel and off-gas air discharged from the fuel cell;
a raw fuel path (30A) for flowing raw fuel toward the reformer;
functional products (32, 33) provided upstream of the reformer in the raw fuel route;
a reformed fuel path (30B) for flowing the reformed fuel generated in the reformer to the fuel cell;
a circulation path (60) that returns a portion of the reformed fuel flowing through the reformed fuel path upstream of the functional product in the raw fuel path;
a flow rate adjustment member (61) that adjusts the flow rate of the reformed fuel flowing through the circulation path;
a control device (100) that controls the flow rate adjustment member;
A heat exchange device (63) that radiates heat from the reformed fuel flowing through the circulation path ,
The reformer is configured to receive heat from the combustor, and
The raw fuel route is provided with a fuel cutoff member (31) that blocks introduction of raw fuel from the outside into the raw fuel route upstream of the connection point with the circulation route,
The control device controls the flow rate adjustment member to throttle the flow rate of the reformed fuel returned from the circulation path to the raw fuel path when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds a predetermined temperature. is controlled so that if the heat exchange device does not operate normally when the temperature of the reformed fuel returned from the circulation path to the raw fuel path exceeds the predetermined temperature, the circulation path is in a fully closed state. While controlling the flow rate adjustment member, the fuel pump (32) that supplies raw fuel to the reformer and the oxidant gas pump (21) that supplies oxidant gas to the fuel cell are stopped, and A fuel cell system that controls the fuel cutoff member so that introduction of raw fuel into the fuel path is cut off .

Images