fuel cell system

Abstract

To provide a fuel cell system with which, of a simple structure though, it is possible to adjust the temperatures of exhaust and circulation gases.SOLUTION: The fuel cell system comprises: a fuel cell 10; a fuel supply channel 30 that supplies a fuel gas to the fuel cell; a reformer 33 that reforms a raw material for reformation to a fuel gas; a fuel circulation channel 40 that guides some of the fuel gas flowing from the reformer toward the fuel cell to the upstream side above the reformer as a circulation gas; a combustor 53 that generates an exhaust gas; an exhaust gas channel 54 that guides the exhaust gas to the outside; a first heat exchange unit 41 that causes the circulation gas and the air to be heat exchanged so as to adjust the temperature of the circulation gas; a second heat exchange unit 60 that causes the exhaust gas flowing in the exhaust gas channel and the air to be heat exchanged so as to adjust the temperature of the exhaust gas; and a blower 70 that blows out the air that is used for heat exchange in the first and second heat exchange units. The first and second heat exchange units are arranged at a position where these units overlap at least in part in the direction of air flow.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Conventionally, a fuel cell system has been known that includes a fuel cell, a reformer that reforms a raw material for reforming into a reformed gas, and a combustor that burns fuel off-gas and oxidant off-gas discharged from the fuel cell to generate a combustion exhaust gas that heats the reformer (see, for example, Patent Document 1). The fuel cell system described in Patent Document 1 includes two heat exchangers: a first heat exchanger that cools the combustion exhaust gas generated in the combustor, and a second heat exchanger that cools a recycled gas that flows through a recycled gas pipe that returns a portion of the reformed gas reformed in the reformer to the inlet side of the reformer.

[0003] The first heat exchanger is connected to a hot water storage tank that stores hot water, a hot water circulation line through which the hot water flows, and a hot water circulation pump that circulates the hot water, and exchanges heat between the hot water circulated by the hot water circulation pump and the combustion exhaust gas. The second heat exchanger is connected to a water tank that stores reforming water, a water supply pipe through which the reforming water flows, and the reforming water pump that circulates the reforming water, and exchanges heat between the reforming water circulated by the reforming water pump and the recycled gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-12488 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a configuration in which two heat exchangers use different refrigerants to adjust the temperatures of the exhaust gas and recycled gas, respectively, as in the fuel cell system described in Patent Document 1, the number of components of the fuel cell system increases, which leads to an increase in the size of the system and an increase in manufacturing costs. Hereinafter, the gas generated in the combustor will also be referred to as exhaust gas, and the gas that is reformed in the reformer and returned to the inlet side of the reformer will be referred to as circulation gas.

[0006] An object of the present disclosure is to provide a fuel cell system that is capable of adjusting the temperatures of exhaust gas and circulating gas with a simple configuration. [Means for solving the problem]

[0007] The invention described in claim 1 is 1. A fuel cell system, comprising: a fuel cell (10) that outputs electrical energy through an electrochemical reaction between a fuel gas and an oxidant gas; a fuel supply passage (30) for supplying fuel gas to the fuel cell; a reformer (33) that reforms the reforming material flowing through the fuel supply passage into a fuel gas and supplies the fuel gas to the fuel cell; a fuel circulation flow path (40) that guides a portion of the fuel gas flowing from the reformer toward the fuel cell as a circulation gas to a portion of the fuel supply flow path upstream of the reformer; a combustor (53) that combusts fuel off-gas and oxidant off-gas discharged from the fuel cell to generate exhaust gas; an exhaust gas flow path (54) connected to the combustor and configured to guide exhaust gas generated in the combustor to the outside of the fuel cell system; a first heat exchange section (41) that exchanges heat between the circulation gas and air to adjust the temperature of the circulation gas; The exhaust gas is heated by exchanging heat with the air flowing through the exhaust gas passage. Temperature a second heat exchange section (60) for adjusting the a blower (70) that blows out air used for heat exchange in the first heat exchange section and the second heat exchange section; The first heat exchange unit and the second heat exchange unit are arranged at positions where they at least partially overlap each other in the air flow direction, which is the direction in which the air blown out by the fan flows.

[0008] This allows the temperature of the circulating gas to be adjusted by exchanging heat between the circulating gas and the air blown out by the fan in the first heat exchanger, and the temperature of the circulating gas to be adjusted by exchanging heat between the exhaust gas and the air blown out by the fan in the second heat exchanger. Therefore, the temperatures of the exhaust gas and the circulating gas can be adjusted with a simpler configuration than when the first heat exchanger and the second heat exchanger are configured to adjust the temperatures of the exhaust gas and the circulating gas using different refrigerants.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. [Figure 2] 1 is a schematic diagram showing a control device of a fuel cell system according to a first embodiment. [Figure 3] 3 is a flowchart showing a control process executed by a control device of the fuel cell system of the first embodiment. [Figure 4] 10A and 10B are diagrams showing the relationship between the rotation speed of the blower fan and the circulating gas temperature and the relationship between the rotation speed of the blower fan and the exhaust gas temperature when the outside air temperature is high. [Figure 5] 10A and 10B are diagrams showing the relationship between the rotation speed of the blower fan and the circulating gas temperature and the relationship between the rotation speed of the blower fan and the exhaust gas temperature when the outside air temperature is low. [Figure 6] FIG. 10 is a schematic diagram of a fuel cell system according to a second embodiment. [Figure 7] FIG. 10 is a schematic diagram of a fuel cell system according to a third embodiment. [Figure 8] FIG. 10 is a diagram comparing the circulation gas temperature in the second embodiment with the circulation gas temperature in the third embodiment. [Figure 9] FIG. 10 is a schematic configuration diagram of a fuel cell system according to a fourth embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a control device of a fuel cell system according to a fourth embodiment. [Figure 11] 10 is a flowchart showing a control process executed by a control device of a fuel cell system according to a fourth embodiment. [Figure 12] FIG. 10 is a schematic configuration diagram of a fuel cell system according to a fifth embodiment. [Figure 13] FIG. 10 is a schematic configuration diagram of a fuel cell system according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0012] (First embodiment) This embodiment will be described with reference to Figures 1 to 5. As shown in Figure 1, a fuel cell system 1 of this embodiment includes a solid oxide fuel cell 10. The solid oxide fuel cell 10 is generally called SOFC (short for Solid Oxide Fuel Cell), and has a high operating temperature (for example, 500°C to 1000°C).

[0013] The fuel cell 10 has a stack structure in which a plurality of power generation cells are stacked, each of which outputs electrical energy through an electrochemical reaction between a fuel gas and an oxidant gas (oxygen from the air in this example). The power generation cells may be either flat or cylindrical in shape.

[0014] Although not shown, the power generation cell is composed of a solid oxide electrolyte, an air electrode (i.e., cathode), and a fuel electrode (i.e., anode). The power generation cell uses hydrogen and carbon monoxide produced by reforming city gas (i.e., gas mainly composed of methane), which is a hydrocarbon fuel, as fuel gas. Note that the fuel used may be gas other than city gas, as long as it is a hydrocarbon gas.

[0015] The fuel cell 10 outputs electrical energy through the electrochemical reactions of hydrogen and oxygen shown in the following reaction formulas F1 and F2.

[0016] (Fuel electrode)2H2+2O 2- →2H2O+4e - …(F1)

[0017] (Air electrode) O2+4e - →2O 2- …(F2) The fuel cell 10 also outputs electrical energy through the electrochemical reactions of carbon monoxide and oxygen shown in the following reaction formulas F3 and F4.

[0018] (Fuel electrode)2CO+2O 2- →2CO2+4e - …(F3)

[0019] (Air electrode) O2+4e - →2O 2- …(F4) Although not shown, the fuel cell 10 is arranged inside a housing having thermal insulation properties together with a reformer 33, a combustor 53, and the like, which will be described later.

[0020] An air supply flow path 20, which is an air distribution path, is connected to an air inlet portion 10a of the fuel cell 10. The air supply flow path 20 is configured by piping or the like. The air supply flow path 20 is provided with a pressure blower (not shown) that pressure-feeds air to the fuel cell 10, and an air preheater (not shown) that heats the air to be supplied to the fuel cell 10. Air heated by the air preheater is supplied to the air inlet portion 10a of the fuel cell 10 by the pressure blower.

[0021] Meanwhile, a fuel supply flow path 30, which is a distribution path for fuel and fuel gas, is connected to the fuel inlet portion 10b of the fuel cell 10. The fuel supply flow path 30 is formed of piping, etc. A fuel pump 31, a desulfurizer 32, and a reformer 33 are provided in this order from the upstream side in the fuel supply flow path 30.

[0022] The fuel pump 31 is a pump for supplying fuel, which is a raw material for reforming, supplied from outside the system toward the fuel cell 10. The fuel pump 31 discharges the sucked fuel toward the downstream side of the fuel supply flow path 30. The fuel pump 31 is configured as an electric pump whose operation is controlled by a control signal from the control device 100.

[0023] The desulfurizer 32 is a device for removing sulfur components contained in the fuel supplied from the fuel pump 31. The desulfurizer 32 in this embodiment is a hydrodesulfurizer that removes sulfur components from the raw fuel by reacting the sulfur components contained in the fuel with hydrogen. The hydrodesulfurizer is configured, for example, by filling a container with a hydrodesulfurizing agent. As the hydrodesulfurizing agent, for example, a CuZn-based catalyst that has both the function of converting sulfur compounds to hydrogen sulfide and the function of adsorbing hydrogen sulfide may be used.

[0024] The hydrodesulfurization agent is not limited to this, and may be composed of, for example, a CoMo-based catalyst that converts sulfur compounds in the fuel into hydrogen sulfide, and at least one of a ZnO-based catalyst and a CuZn-based catalyst that serve as adsorbents that adsorb the converted hydrogen sulfide.

[0025] Here, the desulfurizer 32, which is a hydrodesulfurizer, tends to be able to remove a larger amount of sulfur components as the temperature of the hydrodesulfurizing agent filled therein increases. For this reason, the desulfurizer 32 is used in a heated state. The desulfurizer 32 may be configured to be heated by a heating means such as an electric heater. Alternatively, the desulfurizer 32 may be configured to be heated using exhaust gas generated in a combustor 53, which will be described later, as a heat source.

[0026] The reformer 33 uses steam to reform the fuel supplied from the fuel pump 31 to generate fuel gas. The reformer 33 is configured to include a steam reforming catalyst containing a precious metal such as rhodium or ruthenium.

[0027] Specifically, the reformer 33 heats a mixed gas of fuel and steam, and generates fuel gas (hydrogen, carbon monoxide) through the reforming reaction shown in the following reaction formula F5 and the shift reaction shown in the following reaction formula F6.

[0028] CH4+H2O→CO+H2…(F5) CO+H2O→CO2+H2…(F6) Here, the steam reforming in the reformer 33 is an endothermic reaction, and has the characteristic that the reforming rate improves under high temperature conditions. For this reason, the reformer 33 is used in a heated state. For example, the reformer 33 may be disposed around the fuel cell 10 so as to be able to absorb heat (radiant heat) emitted to the surroundings when the fuel cell 10 generates power. Alternatively, the reformer 33 may be configured to be heated using exhaust gas generated in the combustor 53 (described later) as a heat source.

[0029] Although not shown, a water supply path is connected to the fuel supply flow path 30 between the fuel pump 31 and the reformer 33, and this water supply path is provided with a water pump that supplies water from outside the system and a vaporizer that generates water vapor to be supplied to the reformer 33.

[0030] A fuel circulation flow path 40 is connected to the fuel supply flow path 30, and circulates a portion of the fuel gas flowing downstream of the reformer 33 to the upstream side of the fuel pump 31 in the fuel supply flow path 30. The upstream end of the fuel circulation flow path 40 is connected to the fuel supply flow path 30 downstream of the reformer 33, and the downstream end is connected to the fuel supply flow path 30 upstream of the fuel pump 31, so that a portion of the fuel gas generated in the reformer 33 returns to the upstream side of the fuel pump 31.

[0031] The fuel circulation flow path 40 is provided with a first heat exchanger 41 that exchanges heat between the fuel gas flowing through the fuel circulation flow path 40 and air, a circulation gas regulating valve 42 that controls the flow rate of the fuel gas flowing through the fuel circulation flow path 40, and a circulation gas temperature detector 43 that detects the temperature of the fuel gas flowing through the fuel circulation flow path 40. Hereinafter, the fuel gas flowing through the fuel circulation flow path 40 will also be referred to as circulation gas.

[0032] The first heat exchanger 41 is a condenser that adjusts the temperature of the circulating gas by exchanging heat between the circulating gas and air blown by a blower 70 (described later), and condenses the moisture contained in the circulating gas. Specifically, the first heat exchanger 41 condenses the circulating gas containing water vapor supplied from the vaporizer into liquid water, thereby separating the circulating gas into liquid water and gas.

[0033] The circulation gas adjustment valve 42 is a flow rate adjustment member that adjusts the flow rate of the circulation gas. Adjusting the flow rate of the circulation gas includes setting the flow rate of the circulation gas to zero. The circulation gas adjustment valve 42 opens and closes the fuel circulation flow path 40 and can adjust the valve opening. The circulation gas adjustment valve 42 is configured as an electromagnetic valve whose operation is controlled by a control signal from the control device 100. In this embodiment, the circulation gas adjustment valve 42 functions as a circulation gas adjustment unit.

[0034] As a flow rate adjusting member for adjusting the flow rate of the circulating gas, an electric pump for adjusting the flow rate of the fuel gas flowing through the fuel circulation flow path 40 may be provided instead of the circulating gas adjustment valve 42. In this case, the rotation speed of the electric pump is controlled by a control signal from the control device 100.

[0035] The circulating gas temperature detection unit 43 is a temperature sensor that detects the temperature of the circulating gas that has exchanged heat with the air in the first heat exchange unit 41. The circulating gas temperature detection unit 43 is provided downstream of the first heat exchange unit 41 in the fuel circulation flow path 40, and detects the temperature of the circulating gas that has passed through the first heat exchange unit 41. The circulating gas temperature detection unit 43 is connected to the control device 100, and outputs a detection signal corresponding to the detected temperature of the circulating gas to the control device 100. Hereinafter, the temperature of the circulating gas will also be referred to as the circulating gas temperature Ta.

[0036] The circulating gas temperature detector 43 may be provided inside the first heat exchanger 41 and configured to detect the temperature of the circulating gas when it is discharged from the first heat exchanger 41.

[0037] An off-gas pipe 50 through which the off-gas discharged from the fuel cell 10 flows is also connected to the fuel cell 10. Specifically, an air exhaust pipe 51 through which the oxidant off-gas discharged from the fuel cell 10 flows is connected to the air outlet 10c of the fuel cell 10. A fuel exhaust pipe 52 through which the fuel off-gas discharged from the fuel cell 10 flows is also connected to the fuel outlet 10d of the fuel cell 10.

[0038] A combustor 53 is also connected to the off-gas piping 50. The combustor 53 generates combustion gas by burning fuel or fuel off-gas. For example, during power generation by the fuel cell 10, the combustor 53 generates combustion gas by burning a mixed gas of oxidant off-gas and fuel off-gas as combustible gas. Although not shown, the combustor 53 has a burner for burning the fuel off-gas. In the combustor 53, the fuel off-gas is combusted by igniting the burner, and high-temperature exhaust gas is generated.

[0039] An exhaust gas flow path 54 that discharges high-temperature exhaust gas to the outside of the fuel cell system 1 is connected to the combustor 53. The exhaust gas flow path 54 is provided with a second heat exchanger 60 that exchanges heat between the exhaust gas flowing through the exhaust gas flow path 54 and air, and an exhaust gas temperature detector 61 that detects the temperature of the exhaust gas flowing through the exhaust gas flow path 54.

[0040] The second heat exchanger 60 is a heat exchanger that adjusts the temperature of the exhaust gas by exchanging heat between the exhaust gas and air blown by the blower 70, which will be described later. Specifically, the second heat exchanger 60 is a radiator that radiates heat from the high-temperature combustion gas generated in the combustor 53 by exchanging heat with the air blown by the blower 70.

[0041] The exhaust gas temperature detection unit 61 is a temperature sensor that detects the temperature of the exhaust gas that has undergone heat exchange with air in the second heat exchange unit 60. The exhaust gas temperature detection unit 61 is disposed downstream of the second heat exchange unit 60 in the exhaust gas flow path 54, and detects the temperature of the exhaust gas that has passed through the second heat exchange unit 60. The exhaust gas temperature detection unit 61 is connected to the control device 100, and outputs a detection signal corresponding to the detected exhaust gas temperature to the control device 100. Hereinafter, the temperature of the exhaust gas will also be referred to as the exhaust gas temperature To.

[0042] The exhaust gas temperature detection unit 61 may be provided inside the second heat exchange unit 60 and configured to detect the temperature of the exhaust gas when it is discharged from the second heat exchange unit 60.

[0043] The fuel cell system 1 also includes a blower 70 that blows air toward the first heat exchanger 41 and the second heat exchanger 60, and a duct 71 through which the air blown out by the blower 70 flows.

[0044] The blower 70 is a blower device that draws in air taken into the fuel cell system 1 from outside the system and blows out the drawn-in air to generate an airflow. The blower 70 of this embodiment is configured, for example, as an axial fan that draws in air from a direction along the fan axis and blows it out in a direction along the fan axis. Hereinafter, the direction in which the air blown out by the blower 70 flows is also referred to as the air flow direction.

[0045] The blower 70 has a blower fan 70a that rotates to generate an airflow, and a motor 70b that rotates the blower fan 70a. The blower 70 is configured as an electric blower that drives the blower fan 70a with the motor 70b. The blower fan 70a rotates by the driving force transmitted from the motor 70b, thereby generating an airflow.

[0046] The blower 70 of this embodiment is provided inside the duct 71 and blows out the drawn air downstream in the air flow direction of the duct 71. The motor 70b of the blower 70 is electrically connected to the control device 100, and the rotation speed (i.e., the blowing capacity) of the blower fan 70a is controlled by a control signal sent from the control device 100 to the motor 70b.

[0047] The duct 71 is an airflow path forming section through which air blown out by the blower 70 flows. The blower 70, the first heat exchanger 41, and the second heat exchanger 60 are arranged inside the duct 71. Specifically, the blower 70, the first heat exchanger 41, and the second heat exchanger 60 are arranged in this order inside the duct 71 along the airflow direction. The first heat exchanger 41 and the second heat exchanger 60 are arranged inside the duct 71 so that at least a portion of each of them overlaps with each other in the airflow direction. Therefore, as shown in FIG. 1 , the blown air A blown out by the blower 70 passes through the first heat exchanger 41 and then flows into the second heat exchanger 60. That is, the first heat exchanger 41 and the second heat exchanger 60 are arranged in series along the airflow direction.

[0048] In this embodiment, the first heat exchange unit 41 and the second heat exchange unit 60 are arranged in series so that they completely overlap each other in the air flow direction inside the duct 71. That is, the first heat exchange unit 41 and the second heat exchange unit 60 are arranged so that they overlap each other when projected from one side of the duct 71 to the other side in the air flow direction.

[0049] The blower 70 is disposed upstream in the airflow direction of the first heat exchanger 41 and the second heat exchanger 60. The first heat exchanger 41 is disposed upstream in the airflow direction of the second heat exchanger 60. More specifically, the first heat exchanger 41 and the second heat exchanger 60 are disposed inside the duct 71 so as to overlap each other in the airflow direction.

[0050] Therefore, the blown air A blown out from the blower 70 is blown out to the first heat exchange section 41, where it is heat exchanged, and then flows into the second heat exchange section 60.

[0051] The first heat exchange section 41 and the second heat exchange section 60 may be arranged inside the duct 71 so that only a portion of each section overlaps the other in the air flow direction.

[0052] Next, the control device 100 will be described with reference to Fig. 2. 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 control programs stored in the memory, and controls the operation of various control devices connected to the output side.

[0053] 2, various sensors including a circulation gas temperature detector 43 and an exhaust gas temperature detector 61 are connected to the input side of the control device 100, and detection signals corresponding to the detection results of the various sensors are input to the control device 100. An operation panel (not shown) is also connected to the control device 100. This operation panel is provided with an operation switch for turning on and off power generation by the fuel cell 10, a display for displaying the operating status of the fuel cell 10, etc.

[0054] On the other hand, connected to the output side of the control device 100 are control devices such as a pressure blower (not shown), fuel pump 31, circulation gas regulating valve 42, motor 70b of blower 70, and a burner (not shown) of combustor 53. The operations of these control devices are controlled in response to control signals output from the control device 100.

[0055] Next, we will explain the basic operation of the fuel cell system 1. When an operation switch (not shown) is turned on, the fuel cell system 1 executes a power generation process by the control device 100, which causes the fuel cell 10 to output electrical energy.

[0056] In this power generation process, for example, a pressure blower and a fuel pump 31 (not shown) are controlled so that amounts of oxidant gas and fuel gas appropriate for power generation are supplied to the fuel cell 10. Also, in the power generation process, a blower 70 generates blown air A for cooling exhaust gas generated in the combustor 53 during power generation by the fuel cell 10.

[0057] The fuel discharged from the fuel pump 31 is heated by the heated desulfurizer 32 as it passes through the desulfurizer 32, and sulfur components contained in the fuel are removed by a desulfurizing agent filled in the desulfurizer 32. The fuel from which the sulfur components have been removed in the desulfurizer 32 is mixed with steam generated in a vaporizer (not shown) and flows into the reformer 33. When a mixed gas of fuel and steam is supplied to the reformer 33, fuel gas (hydrogen, carbon monoxide) is generated by the reactions shown in the above-mentioned reaction formulas F5 and F6. The fuel gas generated by the endothermic reaction is heated to a temperature higher than the temperature of the fuel flowing into the reformer 33.

[0058] When the circulation gas regulating valve 42 is closed, the fuel gas generated in the reformer 33 does not flow into the fuel circulation flow path 40, and all of the fuel gas flows into the fuel cell 10. In contrast, when the circulation gas regulating valve 42 is open, part of the fuel gas generated in the reformer 33 is guided to the fuel circulation flow path 40 as circulation gas, and the remaining fuel gas flows into the fuel cell 10.

[0059] The circulating gas flowing through the fuel circulation flow path 40 is cooled by heat exchange with air blown by the blower 70 in the first heat exchanger 41, and is condensed and separated into liquid water and gas, which are returned to the fuel supply flow path 30. The circulating gas temperature detector 43 detects the circulating gas temperature Ta after flowing through the fuel circulation flow path 40 and passing through the first heat exchanger 41, and transmits a detection signal corresponding to the circulating gas temperature Ta to the control device 100.

[0060] Furthermore, air containing oxidant gas blown out from a pressure blower (not shown) flows into the fuel cell 10 via the air supply flow path 20 .

[0061] When supplied with oxidant gas and fuel gas, 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 oxidant off-gas.

[0062] The oxidant off-gas discharged from the fuel cell 10 is led to the combustor 53 via the air discharge pipe 51. The off-gas fuel discharged from the fuel cell 10 flows through the fuel discharge pipe 52 and is led to the combustor 53.

[0063] The oxidant off-gas and off-gas fuel introduced into the combustor 53 are combusted as combustible gas in the combustor 53 to generate high-temperature exhaust gas. The high-temperature exhaust gas generated in the combustor 53 flows through the exhaust gas flow path 54.

[0064] The exhaust gas flowing through the exhaust gas flow path 54 is cooled by heat exchange with air blown by the blower 70 in the second heat exchanger 60. The exhaust gas temperature detector 61 detects the temperature To of the exhaust gas after it flows through the exhaust gas flow path 54 and passes through the second heat exchanger 60, and transmits a detection signal corresponding to the exhaust gas temperature To to the control device 100. The exhaust gas cooled after passing through the second heat exchanger 60 is discharged outside the system as exhaust gas.

[0065] The steam reforming carried out in the reformer 33 is an endothermic reaction, and has the characteristic that the higher the temperature of the reformer 33 itself, the higher the reforming rate. However, if the temperature of the reformer 33 itself is low, carbon is more likely to be deposited on the steam reforming catalyst. This carbon deposition in the reformer 33 can cause deterioration of the steam reforming catalyst and blockage of the path through which the fuel gas flows.

[0066] In contrast, in the fuel cell system 1 of this embodiment, when the circulation gas adjustment valve 42 is open, in addition to the fuel supplied from the outside, circulation gas returned to the fuel supply passage 30 via the fuel circulation passage 40 flows into the reformer 33. This circulation gas returned to the fuel supply passage 30 is part of the fuel gas that is heated and generated in the desulfurizer 32 and the reformer 33 when the fuel cell 10 performs power generation processing. Therefore, when the temperature of the circulation gas is higher than the temperature of the fuel supplied from the outside, the circulation gas increases the temperature of the fuel flowing into the reformer 33, and the desulfurization agent in the reformer 33 can be heated.

[0067] Here, the temperature of the fuel supplied from outside is generally about the same as the temperature outside the fuel cell system 1, that is, the environmental temperature of the location where the fuel cell system 1 is installed. Therefore, if the circulation gas temperature Ta is higher than the environmental temperature, the temperature of the fuel flowing into the reformer 33 can be increased to heat the reformer 33.

[0068] The circulation gas temperature Ta can be increased as the amount of heat dissipated from the circulation gas to the air during heat exchange between the circulation gas and the air in the first heat exchange section 41 decreases. Therefore, the smaller the amount of heat dissipated from the circulation gas to the air in the first heat exchange section 41, the more the temperature of the reformer 33 can be increased. Increasing the temperature of the reformer 33 makes it more difficult for carbon to deposit on the steam reforming catalyst of the reformer 33. Therefore, the more the rotation speed of the blower fan 70a of the blower 70 is reduced to reduce the blowing capacity of the blower 70, the more carbon deposition in the reformer 33 can be suppressed.

[0069] However, when the circulating gas flows into the fuel supply passage 30, the circulating gas is mixed with the fuel and cooled. When the circulating gas is cooled, the water contained in the circulating gas becomes condensed water, which flows together with the fuel to the fuel pump 31. However, if the condensed water flows into the fuel pump 31, there is a risk that the fuel pump 31 will malfunction.

[0070] Condensed water is more likely to be generated when the circulating gas and fuel are mixed together as the difference between the circulating gas temperature Ta and the temperature of the fuel supplied from the outside increases. In other words, the higher the temperature Ta of the circulating gas that has passed through the first heat exchanger 41, the more likely condensed water is to be generated when the circulating gas and fuel are mixed together.

[0071] Therefore, there is a concern that the more the blowing capacity of the blower 70 is reduced to reduce the amount of heat dissipated from the circulating gas to the air in the first heat exchange section 41 in order to avoid carbon deposition in the reformer 33, the more likely condensed water will flow into the fuel pump 31.

[0072] Furthermore, reducing the blowing capacity of the blower 70 also reduces the amount of heat dissipated from the exhaust gas to the air in the second heat exchanger 60. This causes the exhaust gas to be discharged to the outside of the system to become hot. Therefore, reducing the blowing capacity of the blower 70 to avoid carbon deposition in the reformer 33 raises concerns that the temperature of the exhaust gas may become too high.

[0073] Therefore, in the fuel cell system 1 of this embodiment, the control device 100 executes the control process shown in Fig. 3 in order to resolve the above concerns while avoiding carbon deposition in the reformer 33. The control device 100 repeatedly executes the control process described below at predetermined control intervals.

[0074] First, in step S10, the control device 100 determines whether the circulation gas temperature Ta is equal to or higher than a target heating temperature based on a detection signal transmitted from the circulation gas temperature detection unit 43. The target heating temperature is the circulation gas temperature Ta required to increase the temperature of the fuel flowing into the reformer 33 by the circulation gas and suppress the occurrence of carbon deposition in the reformer 33, and is set in advance in the control device 100. In this embodiment, the target heating temperature is set to, for example, 50°C. Note that the target heating temperature may be set to a temperature lower than 50°C (for example, 40°C) or higher than 50°C (for example, 60°C) as long as it is a temperature at which the occurrence of carbon deposition in the reformer 33 can be suppressed.

[0075] The control device 100 executes the process of step S20 when it determines that the circulating gas temperature Ta is not equal to or higher than the target heating temperature based on the detection signal transmitted from the circulating gas temperature detection unit 43. On the other hand, the control device 100 executes the process of step S40 when it determines that the circulating gas temperature Ta is equal to or higher than the target heating temperature.

[0076] In step S20, the control device 100 transmits a control signal to the motor 70b of the blower 70 to reduce the blowing capacity of the blower 70. The blower 70 reduces the blowing capacity based on the control signal transmitted from the control device 100. Specifically, when the control signal to reduce the blowing capacity is transmitted from the control device 100, the blower 70 reduces the rotation speed of the blower fan 70a to reduce the blowing capacity.

[0077] The relationship between the rotation speed of the blower fan 70a and the circulating gas temperature Ta will now be described with reference to Fig. 4. Fig. 4 is a diagram showing the relationship between the rotation speed of the blower fan 70a and the circulating gas temperature Ta and the relationship between the rotation speed of the blower fan 70a and the exhaust gas temperature To, in which the vertical axis represents the circulating gas temperature Ta and the exhaust gas temperature To, and the horizontal axis represents the rotation speed of the blower fan 70a.

[0078] The more the rotation speed of the blower fan 70a is reduced to lower the blowing capacity of the blower 70, the more the volume of air passing through the first heat exchanger 41 per unit time decreases. Therefore, the more the rotation speed of the blower fan 70a is reduced to lower the blowing capacity of the blower 70, the less heat is dissipated from the circulating gas to the air when heat is exchanged between the circulating gas and the air in the first heat exchanger 41. Therefore, by reducing the rotation speed of the blower fan 70a, the circulating gas temperature Ta can be increased, as shown in FIG.

[0079] Furthermore, the more the rotation speed of the blower fan 70a is reduced to lower the blowing capacity of the blower 70, the more the volume of air passing through the second heat exchange section 60 per unit time decreases. Therefore, the more the rotation speed of the blower fan 70a is reduced to lower the blowing capacity of the blower 70, the less heat is dissipated from the circulating gas to the air when heat is exchanged between the circulating gas and the air in the second heat exchange section 60. Therefore, by reducing the rotation speed of the blower fan 70a, the exhaust gas temperature To also increases, as shown in FIG.

[0080] After executing step S20, the control device 100 again determines in step S30 whether the circulating gas temperature Ta is equal to or higher than the target heating temperature based on the detection signal transmitted from the circulating gas temperature detection unit 43. If the control device 100 does not determine that the circulating gas temperature Ta is equal to or higher than the target heating temperature, the control device 100 returns to the control processing of step S20. The control device 100 repeatedly executes steps S20 and S30 until the circulating gas temperature Ta becomes equal to or higher than the target heating temperature. If the control device 100 determines in step S30 that the circulating gas temperature Ta is equal to or higher than the target heating temperature, the control device 100 executes the processing of step S40.

[0081] In step S40, the control device 100 determines whether the circulation gas temperature Ta is lower than the condensation judgment temperature based on the detection signal transmitted from the circulation gas temperature detection unit 43. The control device 100 also determines whether the exhaust gas temperature To is lower than the cooling judgment temperature based on the detection signal transmitted from the exhaust gas temperature detection unit 61. If the control device 100 determines that the circulation gas temperature Ta is lower than the condensation judgment temperature and that the exhaust gas temperature To is lower than the cooling judgment temperature, it executes the process of step S50. On the other hand, if the control device 100 does not determine that the circulation gas temperature Ta is lower than the condensation judgment temperature and that the exhaust gas temperature To is lower than the cooling judgment temperature, it executes the process of step S60.

[0082] The condensation determination temperature is a circulation gas temperature Ta for determining whether the circulation gas is at a temperature at which it is likely to be recondensed when the circulation gas is introduced into the fuel supply flow path 30 and mixed with the fuel flowing through the fuel supply flow path 30, and is set in advance in the control device 100. The condensation determination temperature is the highest temperature at which recondensation of the circulation gas is expected. In this embodiment, the condensation determination temperature is set so that the difference between the circulation gas temperature Ta and the temperature of the fuel supplied from the outside is 15°C.

[0083] The condensation judgment temperature may be set so that the difference between the circulation gas temperature Ta and the temperature of the fuel is greater than 15°C (for example, 20°C) as long as it is a temperature at which it is possible to determine whether the circulation gas is likely to recondense when mixed with fuel. Alternatively, the condensation judgment temperature may be set so that the difference between the circulation gas temperature Ta and the temperature of the fuel is less than 15°C (for example, 10°C).

[0084] The cooling judgment temperature is an exhaust gas temperature To for determining whether the exhaust gas to be discharged to the outside of the system as exhaust gas has been cooled by the second heat exchanger 60 to a cooling temperature necessary for safe discharge, and is set in advance in the control device 100. The cooling judgment temperature is the highest temperature necessary for safe discharge of the exhaust gas. In this embodiment, the cooling judgment temperature is set to, for example, 70°C.

[0085] The cooling judgment temperature may be set to a temperature higher than 70°C (e.g., 80°C) or lower than 70°C (e.g., 60°C), as long as it is a temperature at which it is possible to determine whether the exhaust gas has been cooled to a safe temperature.

[0086] When both the conditions that the circulation gas temperature Ta is lower than the condensation judgment temperature and the exhaust gas temperature To is lower than the cooling judgment temperature are met, the control device 100 executes the process of step S50.

[0087] In step S50, the control device 100 transmits a control signal to the motor 70b of the blower 70 to reduce the blowing capacity of the blower 70. The blower 70 reduces the blowing capacity based on the control signal transmitted from the control device 100. Specifically, when the control signal to reduce the blowing capacity is transmitted from the control device 100, the blower 70 reduces the rotation speed of the blower fan 70a to reduce the blowing capacity.

[0088] As described above, when the rotation speed of the blower fan 70a is reduced, the amount of heat dissipated from the circulating gas to the air when heat is exchanged between the circulating gas and the air in the first heat exchange section 41 decreases, and the circulating gas temperature Ta further increases.

[0089] Furthermore, when the rotation speed of the blower fan 70a is reduced, as described above, the amount of heat dissipated from the exhaust gas to the air during heat exchange between the exhaust gas and the air in the second heat exchange section 60 decreases, further increasing the exhaust gas temperature To. Furthermore, by reducing the rotation speed of the blower fan 70a, the power consumption required to operate the blower 70 is reduced.

[0090] The rotation speed of the blower fan 70a set in step S50 is set in advance through experiments or the like so that reducing the rotation speed of the blower fan 70a brings the circulation gas temperature Ta closer to the condensation judgment temperature and the exhaust gas temperature To closer to the cooling judgment temperature. The rotation speed of the blower fan 70a set in step S50 is determined so that, when the rotation speed of the blower fan 70a is reduced, the circulation gas temperature Ta falls within a range that does not exceed the condensation judgment temperature and the exhaust gas temperature To falls within a range that does not exceed the cooling judgment temperature. The rotation speed of the blower fan 70a set in step S50 is set in advance in the control device 100 to a different value depending on the circulation gas temperature Ta detected by the circulation gas temperature detection unit 43 and the exhaust gas temperature To detected by the exhaust gas temperature detection unit 61.

[0091] 4, the rotation speed of the blower fan 70a when the exhaust gas temperature To becomes the cooling judgment temperature is greater than the rotation speed of the blower fan 70a when the circulation gas temperature Ta becomes the condensation judgment temperature. Therefore, the rotation speed of the blower fan 70a set in step S50 is set so that the circulation gas temperature Ta is equal to or higher than the target heating temperature and the exhaust gas temperature To is lower than the cooling judgment temperature. For example, the rotation speed of the blower fan 70a set in step S50 may be set so that the exhaust gas temperature To becomes closest to the cooling judgment temperature.

[0092] As a result, as shown in Fig. 4, the circulating gas temperature Ta is controlled by the blower 70 so as to approach the condensation judgment temperature. The exhaust gas temperature To is also controlled by the blower 70 so as to approach the cooling judgment temperature. In other words, the control device 100 controls the blower 70 so as to bring the circulating gas temperature Ta closer to the condensation judgment temperature, and also controls the blower 70 so as to bring the exhaust gas temperature To closer to the cooling judgment temperature. Then, by reducing the rotation speed of the blower fan 70a so that the exhaust gas temperature To is closest to the cooling judgment temperature, the power consumption required to operate the blower 70 is reduced.

[0093] The condensation judgment temperature and the cooling judgment temperature are affected by the temperature outside the fuel cell system 1, the temperature of the fuel supplied from the outside, the amount of power generated by the fuel cell 10 (i.e., the flow rate of the fuel gas flowing through the fuel supply flow path 30), etc. Therefore, the relationship between the rotation speed of the blower fan 70a and the circulating gas temperature Ta and the relationship between the rotation speed of the blower fan 70a and the exhaust gas temperature To are not limited to those shown in Fig. 4. Furthermore, the target heating temperature, the condensation judgment temperature, and the cooling judgment temperature are not limited to those shown in Fig. 4.

[0094] For example, assume that Fig. 4 shows an example of a high outdoor temperature, which is the relationship between the rotation speed of the blower fan 70a and the circulating gas temperature Ta and the relationship between the rotation speed of the blower fan 70a and the exhaust gas temperature To when the ambient temperature is relatively high, such as in summer. Also assume that Fig. 5 shows an example of a low outdoor temperature, which is the relationship between the rotation speed of the blower fan 70a and the circulating gas temperature Ta and the relationship between the rotation speed of the blower fan 70a and the exhaust gas temperature To when the ambient temperature is relatively low, such as in winter.

[0095] In this case, the temperature of the air blown by the blower 70 and the temperature of the fuel supplied from the outside are lower at low outdoor temperatures than at high outdoor temperatures. Therefore, under the same rotation speed of the blower fan 70a, the amount of heat dissipated from the circulating gas to the air when heat is exchanged between the circulating gas and the air in the first heat exchanger 41 is greater at low outdoor temperatures than at high outdoor temperatures. Also, under the same rotation speed of the blower fan 70a, the amount of heat dissipated from the exhaust gas to the air when heat is exchanged between the exhaust gas and the air in the second heat exchanger 60 is greater at low outdoor temperatures than at high outdoor temperatures.

[0096] 4 and 5, the rotation speed of the blower fan 70a for setting the circulation gas temperature Ta to the target heating temperature is smaller when the outdoor temperature is low than when the outdoor temperature is high. Also, the rotation speed of the blower fan 70a for setting the circulation gas temperature Ta to the condensation judgment temperature is smaller when the outdoor temperature is low than when the outdoor temperature is high. And the rotation speed of the blower fan 70a for setting the exhaust gas temperature To to the cooling judgment temperature is smaller when the outdoor temperature is low than when the outdoor temperature is high.

[0097] 5, the rotation speed of the blower fan 70a when the exhaust gas temperature To becomes the cooling judgment temperature is assumed to be smaller than the rotation speed of the blower fan 70a when the circulation gas temperature Ta becomes the condensation judgment temperature. In this case, the rotation speed of the blower fan 70a set in step S50 is set so that the circulation gas temperature Ta is equal to or higher than the target heating temperature and lower than the condensation judgment temperature. For example, the rotation speed of the blower fan 70a set in step S50 may be set so that the circulation gas temperature Ta becomes closest to the condensation judgment temperature.

[0098] The control device 100 controls the blower 70 so that the circulation gas temperature Ta approaches the condensation judgment temperature, and also controls the blower 70 so that the exhaust gas temperature To approaches the cooling judgment temperature. By reducing the rotation speed of the blower fan 70a, the power consumption for operating the blower 70 is reduced.

[0099] If the rotation speed of the blower fan 70a when the exhaust gas temperature To becomes the cooling judgment temperature is smaller than the rotation speed of the blower fan 70a when the circulation gas temperature Ta becomes the condensation judgment temperature, the valve aperture of the circulation gas adjustment valve 42 may be reduced. When the valve aperture of the circulation gas adjustment valve 42 is reduced, the circulation gas flowing through the fuel circulation flow path 40 decreases, and therefore, when the rotation speed of the blower fan 70a is constant, the circulation gas temperature Ta decreases.

[0100] This allows the rotation speed of the blower fan 70a when the circulation gas temperature Ta becomes the condensation judgment temperature to be smaller than the rotation speed of the blower fan 70a when the exhaust gas temperature To becomes the cooling judgment temperature. Therefore, the rotation speed of the blower fan 70a set in step S50 can be set so that the exhaust gas temperature To approaches the cooling judgment temperature, thereby further reducing the power consumption for operating the blower 70.

[0101] Furthermore, if the control device 100 determines in step S40 that the circulation gas temperature Ta is lower than the condensation judgment temperature and the exhaust gas temperature To is not lower than the cooling judgment temperature, the control device 100 executes the process of step S60.

[0102] In step S60, the control device 100 transmits a control signal to the motor 70b of the blower 70 to increase the blowing capacity of the blower 70. The blower 70 increases its blowing capacity based on the control signal transmitted from the control device 100. Specifically, when the control signal to increase the blowing capacity is transmitted from the control device 100, the blower 70 increases the rotation speed of the blower fan 70a to increase its blowing capacity. In this way, by increasing the rotation speed of the blower fan 70a, the circulating gas temperature Ta can be reduced. Furthermore, by increasing the rotation speed of the blower fan 70a, the exhaust gas temperature To can be reduced.

[0103] Here, the relationship between the rotation speed of the blower fan 70a and the exhaust gas temperature To will be described with reference to Fig. 4. The more the rotation speed of the blower fan 70a is increased to increase the blowing capacity of the blower 70, the greater the amount of heat dissipated from the circulating gas to the air when heat is exchanged between the circulating gas and the air in the first heat exchange section 41. Furthermore, the more the rotation speed of the blower fan 70a is increased to increase the blowing capacity of the blower 70, the greater the amount of heat dissipated from the exhaust gas to the air when heat is exchanged between the exhaust gas and the air in the second heat exchange section 60. For this reason, as shown in Fig. 4, increasing the rotation speed of the blower fan 70a reduces the circulating gas temperature Ta and the exhaust gas temperature To.

[0104] After executing step S60, in step S70, the control device 100 determines whether the circulating gas temperature Ta is equal to or higher than the condensation judgment temperature based on the detection signal transmitted from the circulating gas temperature detection unit 43. The control device 100 also determines whether the exhaust gas temperature To is equal to or higher than the cooling judgment temperature based on the detection signal transmitted from the exhaust gas temperature detection unit 61.

[0105] The control device 100 repeatedly executes steps S60 and S70 until the circulation gas temperature Ta is equal to or higher than the condensation judgment temperature and the exhaust gas temperature To is equal to or higher than the cooling judgment temperature. If it is determined in step S70 that the circulation gas temperature Ta is equal to or higher than the condensation judgment temperature and the exhaust gas temperature To is equal to or higher than the cooling judgment temperature, the control process ends. As a result, the circulation gas temperature Ta becomes lower than the condensation judgment temperature and the exhaust gas temperature To becomes lower than the cooling judgment temperature.

[0106] As described above, in the fuel cell system 1 of this embodiment, the first heat exchanger 41 and the second heat exchanger 60 are arranged at positions where they overlap each other in the air flow direction.

[0107] This allows the temperature of the circulating gas to be adjusted by heat exchange between the circulating gas and the air blown out by the blower 70 in the first heat exchanger 41, and the temperature of the circulating gas to be adjusted by heat exchange between the exhaust gas and the air blown out by the blower 70 in the second heat exchanger 60. Therefore, the temperatures of the exhaust gas and the circulating gas can be adjusted with a simpler configuration than when the first heat exchanger 41 and the second heat exchanger 60 are configured to adjust the temperatures of the exhaust gas and the circulating gas, respectively, using different refrigerants.

[0108] Furthermore, the amount of condensed water produced when the first heat exchange section 41 condenses the circulation gas can be adjusted by changing the rotation speed of the blower 70, which adjusts the temperature of the exhaust gas and the circulation gas.

[0109] Furthermore, compared to a configuration in which the first heat exchange section 41 and the second heat exchange section 60 do not overlap in the air flow direction, the cross-sectional area of ​​the duct 71 in the direction perpendicular to the air flow direction can be made smaller. That is, the flow path area of ​​the duct 71 can be made smaller. Therefore, even if the flow path area of ​​the duct 71 is made relatively small, it is possible to ensure a sufficient area of ​​the air inlet surface perpendicular to the air flow direction in each of the first heat exchange section 41 and the second heat exchange section 60.

[0110] Furthermore, according to the above embodiment, the following effects can be obtained.

[0111] (1) In the above embodiment, the first heat exchange section 41 is disposed upstream of the second heat exchange section 60 in the air flow direction.

[0112] Here, the first heat exchanger 41 exchanges heat between the circulation gas flowing through the fuel circulation passage 40 and the air. The circulation gas that exchanges heat in the first heat exchanger 41 is a portion of the fuel gas discharged from the reformer 33. In contrast, the second heat exchanger 60 exchanges heat between the exhaust gas flowing through the exhaust gas passage 54 and the air. The exhaust gas that exchanges heat in the second heat exchanger 60 is a fluid generated from the fuel off-gas and oxidant off-gas discharged from the fuel cell 10.

[0113] Therefore, the flow rate of the exhaust gas flowing through the exhaust gas flow path 54 is greater than the flow rate of the circulating gas flowing through the fuel circulation flow path 40. Therefore, the amount of heat exchanged between the circulating gas and the air in the first heat exchange section 41 is smaller than the amount of heat exchanged between the exhaust gas and the air in the second heat exchange section 60.

[0114] That is, the temperature difference between the air flowing into the first heat exchange section 41 and the air discharged from the first heat exchange section 41 is smaller than the temperature difference between the air flowing into the second heat exchange section 60 and the air discharged from the second heat exchange section 60. In other words, the amount of change in temperature of the air that changes when passing through the first heat exchange section 41 is smaller than the amount of change in temperature of the air that changes when passing through the second heat exchange section 60.

[0115] For this reason, if the first heat exchanger 41, through which the temperature of the air changes little as it passes through, is positioned downstream of the second heat exchanger 60, through which the temperature of the air changes much as it passes through, the temperature of the air flowing into the first heat exchanger 41 is likely to deviate significantly from the temperature of the air blown out by the blower 70. This limits the amount of heat dissipated from the circulating gas to the air in the first heat exchanger 41, which may make it difficult to exchange heat between the circulating gas and the air in the first heat exchanger 41.

[0116] In contrast to this, according to this embodiment, the first heat exchange section 41, which experiences a small change in temperature as the air passes through it, is arranged upstream of the second heat exchange section 60 in the air flow direction, which facilitates heat exchange between the circulating gas and the air in the first heat exchange section 41. Furthermore, the air that has passed through the first heat exchange section 41, which experiences a small change in temperature as the air passes through it, can be used to sufficiently exchange heat with the exhaust gas in the second heat exchange section 60.

[0117] (2) In the above embodiment, the blower 70 is disposed upstream of the first heat exchanger 41 in the air flow direction.

[0118] This prevents condensed water generated by condensation of the circulating gas from adhering to the blower 70 when heat exchange between the circulating gas and air occurs in the first heat exchange section 41. This prevents breakdown of the blower 70 due to the adhesion of condensed water.

[0119] (3) In the above embodiment, the system includes an exhaust gas temperature detection unit 61 that detects the exhaust gas temperature To, and a control device 100 that controls the operation of the blower 70. The blower 70 has a blower fan 70a that rotates to generate an airflow. When the exhaust gas temperature To is lower than the cooling determination temperature, the control device 100 reduces the rotation speed of the fan so that the exhaust gas temperature To approaches the necessary cooling determination temperature.

[0120] According to this, by reducing the rotation speed of the blower fan 70a so that the exhaust gas temperature To approaches the cooling judgment temperature, the exhaust gas can be maintained at a temperature state at which it can be discharged while avoiding excessive cooling of the exhaust gas, thereby reducing the power consumption required to operate the blower 70.

[0121] (4) In the above embodiment, the system includes a circulating gas temperature detection unit 43 that detects the circulating gas temperature Ta, and a control device 100 that controls the operation of the blower 70. The blower 70 has a blower fan 70a that rotates to generate an airflow. When the circulating gas temperature Ta is lower than the target heating temperature, the control device 100 increases the rotation speed of the blower fan 70a so that the circulating gas temperature Ta becomes equal to or higher than the heating temperature.

[0122] According to this, by increasing the rotation speed of the blower fan 70a so that the circulating gas temperature Ta becomes equal to or higher than the target heating temperature, the reformer 33 can be heated by the circulating gas to a temperature at which carbon deposition is unlikely to occur.

[0123] (5) In the above embodiment, when the circulating gas temperature Ta is higher than the target heating temperature and lower than the condensation judgment temperature, the control device 100 reduces the rotation speed of the blower fan 70a so that the circulating gas temperature Ta approaches the condensation judgment temperature.

[0124] According to this, by reducing the rotation speed of the blower fan 70a so that the circulating gas temperature Ta approaches the condensation judgment temperature, it is possible to suppress the generation of condensed water when the circulating gas is mixed with fuel while also suppressing the power consumption required to operate the blower 70.

[0125] (Second embodiment) Next, a second embodiment will be described with reference to FIG. 6. In this embodiment, the configuration of the second heat exchange section 60 differs from that of the first embodiment. Other than this, the second embodiment is similar to the first embodiment. Therefore, in this embodiment, the differences from the first embodiment will be mainly described, and descriptions of the same parts as the first embodiment may be omitted.

[0126] As shown in Figure 6, the second heat exchange section 60 of this embodiment has a refrigerant flow path 601 through which the refrigerant flows, a refrigerant circulation section 602 that circulates the refrigerant, an exhaust heat exchanger 603 that exchanges heat between the exhaust gas and the refrigerant, and a radiator 604 that exchanges heat between the refrigerant discharged from the exhaust heat exchanger 603 and air.

[0127] The refrigerant flow path 601 is a refrigerant circuit for circulating the refrigerant in the second heat exchange section 60. In this embodiment, the refrigerant flowing through the refrigerant flow path 601 may be a fluid with a higher heat transfer coefficient than air. For example, LLC containing ethylene glycol may be used as the refrigerant. LLC is an abbreviation for Long Life Coolant.

[0128] The refrigerant circulation unit 602 is a pump for circulating the refrigerant in the refrigerant flow path 601. The refrigerant circulation unit 602 discharges the sucked refrigerant toward the downstream side of the refrigerant flow path 601. The refrigerant circulation unit 602 is configured with an electric pump whose operation is controlled by a control signal from the control device 100.

[0129] The exhaust heat exchanger 603 is a heat exchange unit provided in the exhaust gas flow path 54, and dissipates heat from the exhaust gas by exchanging heat between the exhaust gas flowing through the exhaust gas flow path 54 and the refrigerant flowing through the refrigerant flow path 601. The exhaust heat exchanger 603 has an exhaust-side refrigerant passage 603a through which the refrigerant flows, and an exhaust gas passage 603b through which the exhaust gas flows. The exhaust-side refrigerant passage 603a is connected to the refrigerant flow path 601. The exhaust gas passage 603b is connected to the exhaust gas flow path 54. The exhaust heat exchanger 603 cools the exhaust gas by exchanging heat between the refrigerant flowing through the exhaust-side refrigerant passage 603a and the exhaust gas flowing through the exhaust gas passage 603b.

[0130] In addition, the exhaust gas temperature detection unit 61 in this embodiment is arranged downstream of the exhaust heat exchanger 603 in the exhaust gas flow path 54, and is configured to be able to detect the temperature of the exhaust gas that has passed through the exhaust heat exchanger 603.

[0131] The radiator 604 is a heat dissipation unit that dissipates heat from the refrigerant used for heat exchange in the exhaust heat exchanger 603 by exchanging heat between the refrigerant discharged from the exhaust heat exchanger 603 and the air blown out by the fan 70. The radiator 604 has a heat dissipation-side refrigerant passage 604a through which the refrigerant flows. The heat dissipation-side refrigerant passage 604a is connected to the refrigerant flow path 601.

[0132] The radiator 604 is disposed inside the duct 71. Specifically, the radiator 604 is disposed inside the duct 71 downstream in the air flow direction of the blower 70 and the first heat exchanger 41. The first heat exchanger 41 and the radiator 604 are disposed inside the duct 71 so as to overlap with each other in the air flow direction. That is, the first heat exchanger 41 and the radiator 604 are disposed so as to overlap with each other when projected from one side of the duct 71 to the other side in the air flow direction. Therefore, the blown air A blown out by the blower 70 passes through the first heat exchanger 41 and then flows into the radiator 604. That is, the first heat exchanger 41 and the radiator 604 are disposed in series along the air flow direction.

[0133] The radiator 604 cools the refrigerant by exchanging heat between the air blown out by the fan 70 and the refrigerant flowing through the heat-radiation-side refrigerant passage 604a inside the duct 71.

[0134] According to this, heat exchange between the exhaust gas and the air blown out by the blower 70 is performed via a refrigerant having a higher heat transfer coefficient than the blown air A, which makes it easier to cool the exhaust gas.

[0135] (Third embodiment) Next, a third embodiment will be described with reference to FIGS. 7 and 8. In this embodiment, the positional relationship between the radiator 604 and the first heat exchange section 41 differs from that of the second embodiment. Other than this, the third embodiment is similar to the second embodiment. Therefore, in this embodiment, differences from the second embodiment will be mainly described, and descriptions of similar parts to the second embodiment may be omitted.

[0136] 7, the blower 70, the radiator 604, and the first heat exchanger 41 are arranged in this order along the airflow direction inside the duct 71. That is, the first heat exchanger 41 is arranged downstream in the airflow direction inside the duct 71 from the blower 70 and the radiator 604. Therefore, the blown air A blown out by the blower 70 passes through the radiator 604 and then flows into the first heat exchanger 41.

[0137] The reason for arranging the first heat exchange unit 41 and the radiator 604 in this manner will be described. In the second heat exchange unit 60 of this embodiment, the refrigerant is heated by heat exchange between the high-temperature exhaust gas and the refrigerant in the exhaust heat exchanger 603. Then, the refrigerant heated by heat exchange with the exhaust gas flows into the radiator 604. Therefore, the air blown out from the blower 70 is heated by heat exchange with the heated refrigerant in the radiator 604, and the heat of the exhaust gas is transferred to the air through the refrigerant.

[0138] Therefore, air heated by the heat of the exhaust gas flows into the first heat exchanger 41, which is arranged downstream of the radiator 604 in the air flow direction. This allows the circulating gas to be heated by heat exchange between the heated air and the circulating gas in the first heat exchanger 41. Note that the higher the temperature outside the fuel cell system 1, the higher the temperature of the air heated in the first heat exchanger 41, and therefore the higher the circulating gas temperature Ta.

[0139] In contrast, in the second embodiment in which the radiator 604 is arranged downstream of the first heat exchanger 41 in the air flow direction, air blown out from the blower 70 directly flows into the first heat exchanger 41. Therefore, air at a temperature approximately the same as the temperature outside the fuel cell system 1 flows into the first heat exchanger 41. Therefore, in the second embodiment in which the radiator 604 is arranged downstream of the first heat exchanger 41 in the air flow direction, the temperature of the air flowing into the first heat exchanger 41 is lower than the temperature of the air flowing into the first heat exchanger 41 in the configuration of this embodiment.

[0140] 8, the circulating gas temperature Ta when the radiator 604 is arranged downstream of the first heat exchange section 41 in the air flow direction is lower than the circulating gas temperature Ta when the radiator 604 is arranged upstream of the first heat exchange section 41 in the air flow direction. That is, as shown in FIG. 8, the circulating gas temperature Ta in this embodiment in which the radiator 604 is arranged upstream of the first heat exchange section 41 in the air flow direction is higher than the circulating gas temperature Ta in the configuration of the second embodiment in which the radiator 604 is arranged downstream of the first heat exchange section 41 in the air flow direction.

[0141] In addition, the solid line in FIG. 8 indicates the circulating gas temperature Ta of this embodiment, and the dashed line indicates the circulating gas temperature Ta of the second embodiment.

[0142] Therefore, according to the configuration of the fuel cell system 1 of this embodiment, for example, even when the temperature outside the fuel cell system 1 is relatively low, it is easy to raise the circulation gas temperature Ta to a temperature higher than the target heating temperature. Therefore, it is easy to suppress the occurrence of carbon deposition in the reformer 33.

[0143] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Figures 9 to 11. This embodiment differs from the second embodiment in that it includes an outside air temperature detector 72 that detects the temperature outside the fuel cell system 1, and in that the rotation direction of the blower fan 70a of the blower 70 is switchable between forward and reverse rotation. Other than this, it is the same as the second embodiment. Therefore, in this embodiment, the differences from the second embodiment will be mainly described, and descriptions of the same parts as the second embodiment may be omitted.

[0144] The outside air temperature detection unit 72 is a temperature sensor that detects the temperature outside the fuel cell system 1 (i.e., the environmental temperature where the fuel cell system 1 is installed). The outside air temperature detection unit 72 is installed outside the fuel cell system 1. As shown in FIG. 10, the outside air temperature detection unit 72 is connected to the control device 100, and outputs a detection signal corresponding to the detected temperature outside the fuel cell system 1 to the control device 100. Hereinafter, the temperature outside the fuel cell system 1 will also be referred to as the outside air temperature Ts.

[0145] Furthermore, the blower 70 of this embodiment is configured so that the rotation direction of the motor 70b can be switched between forward and reverse rotation directions by a control voltage output from the control device 100. As a result, the blower 70 of this embodiment can change the flow direction of the blower air A flowing inside the duct 71 by switching the rotation direction of the blower fan 70a in response to switching the rotation direction of the motor 70b.

[0146] In this embodiment, when the blower fan 70a rotates in the forward direction, as shown in Fig. 9, the blown air A1 flows through the first heat exchanger 41 and then into the radiator 604. In this case, the circulating gas is cooled by exchanging heat with the air blown out from the blower 70 in the first heat exchanger 41.

[0147] On the other hand, when the blower fan 70a rotates in the reverse direction, the blown air A2 flows so as to pass through the radiator 604 and then enter the first heat exchanger 41. In this case, the circulating gas is heated in the first heat exchanger 41 by exchanging heat with the air heated by the radiator 604.

[0148] Next, the control process for determining the rotation direction of the blower fan 70a, which is executed by the control device 100 when the fuel cell system 1 executes the power generation process, will be described with reference to FIG.

[0149] First, in step S100, the control device 100 determines whether the outside air temperature Ts is equal to or lower than the rotation determination temperature based on the detection signal transmitted from the outside air temperature detection unit 72. The rotation determination temperature is the outside air temperature Ts at which the outside air temperature Ts is relatively low and heating of the circulating gas is required, and is set in advance in the control device 100. In this embodiment, the rotation determination temperature is set to, for example, 10°C. Note that the rotation determination temperature may be set to a temperature lower than 10°C (for example, 5°C) or a temperature higher than 10°C (for example, 15°C) as long as it is a temperature at which it is possible to determine whether heating of the circulating gas is required.

[0150] If the control device 100 determines that the outside air temperature Ts is not equal to or lower than the rotation determination temperature based on the detection signal transmitted from the outside air temperature detection unit 72, then in step S110, it transmits a control signal to the blower 70 to rotate the blower fan 70a in the forward direction. On the other hand, if it determines that the outside air temperature Ts is equal to or lower than the rotation determination temperature, then in step S120, it transmits a control signal to the blower 70 to rotate the blower fan 70a in the reverse direction.

[0151] 9, when the blower fan 70a rotates in the forward direction, the blown air A1 blown out from the blower 70 flows through the first heat exchanger 41 and then the radiator 604. As a result, the first heat exchanger 41 can cool the circulating gas by exchanging heat between the circulating gas and the air blown out from the blower 70.

[0152] Furthermore, when the blower fan 70a rotates in the reverse direction, the blown air A2 drawn in by the blower 70 flows in this order through the radiator 604 and the first heat exchanger 41. As a result, the first heat exchanger 41 can heat the circulating gas by exchanging heat between the circulating gas and the air heated by the radiator 604.

[0153] According to this, when the outside air temperature Ts is relatively high and the circulating gas needs to be cooled, the circulating gas can be cooled by the air blown out by the blower 70. Also, when the outside air temperature Ts is relatively low and the circulating gas needs to be heated, the circulating gas can be heated by the air heated by the radiator 604.

[0154] (Fifth embodiment) Next, a fifth embodiment will be described with reference to Fig. 12. This embodiment differs from the third embodiment in that the most downstream portion of the exhaust gas flow path 54 is disposed inside the duct 71. Other than this, this embodiment is similar to the third embodiment. Therefore, in this embodiment, the differences from the third embodiment will be mainly described, and a description of the same parts as the third embodiment may be omitted.

[0155] 12, the most downstream portion of exhaust gas flow path 54 in this embodiment is disposed inside duct 71. In other words, when exhaust gas blowout portion 54a is defined as a portion of exhaust gas flow path 54 that blows out exhaust gas flowing through exhaust gas flow path 54 to the outside of exhaust gas flow path 54, exhaust gas blowout portion 54a is disposed inside duct 71. Specifically, exhaust gas blowout portion 54a is disposed inside duct 71 downstream of first heat exchanger 41 and radiator 604 in the air flow direction.

[0156] More specifically, the blower 70, the radiator 604, the first heat exchanger 41, and the exhaust gas outlet 54a are arranged in this order along the air flow direction inside the duct 71. Therefore, as shown in Fig. 12, the blown air A blown out by the blower 70 passes through the radiator 604 and the first heat exchanger 41, and then is mixed with the exhaust gas discharged into the duct 71 from the exhaust gas outlet 54a.

[0157] According to this, the exhaust gas discharged from the exhaust gas blowout section 54a can be further cooled by mixing it with the air that has passed through the radiator 604 and the first heat exchange section 41. Furthermore, even if the exhaust gas contains unreacted fuel gas, by mixing it with the air that has passed through the radiator 604 and the first heat exchange section 41, the concentration of fuel gas contained in the mixed gas can be reduced.

[0158] (Sixth embodiment) Next, a sixth embodiment will be described with reference to Fig. 13. This embodiment differs from the first embodiment in that an off-gas circulation channel 80 is connected to the fuel supply channel 30, and an ejector 81 is provided at the location where the fuel supply channel 30 and the off-gas circulation channel 80 are connected. Other than this, this embodiment is similar to the first embodiment. Therefore, in this embodiment, the differences from the first embodiment will be mainly described, and descriptions of the same parts as the first embodiment may be omitted.

[0159] An off-gas circulation flow path 80 that returns a portion of the fuel off-gas discharged from the fuel cell 10 to the upstream side of the reformer 33 is connected to the fuel discharge pipe 52 in this embodiment. The off-gas circulation flow path 80 in this embodiment has an upstream end connected to the fuel discharge pipe 52 and a downstream end connected to the fuel supply flow path 30 between the desulfurizer 32 and the reformer 33 so that a portion of the fuel off-gas discharged from the fuel cell 10 returns to the upstream side of the reformer 33. Hereinafter, the fuel off-gas flowing through the off-gas circulation flow path 80 will also be referred to as recycled gas.

[0160] Further, the off-gas circulation passage 80 is provided with a recycle flow rate detection unit 82 that detects the flow rate of the recycle gas, and an ejector 81. The recycle flow rate detection unit 82 is connected to the control device 100, and outputs a detection signal to the control device 100 according to the detected flow rate of the recycle gas.

[0161] The ejector 81 is provided at a location where the downstream end of the off-gas circulation passage 80 is connected to the fuel supply passage 30. The ejector 81 uses the fuel flowing through the fuel supply passage 30 as a driving flow to suck in recycled gas and supplies it to the reformer 33 together with the fuel gas.

[0162] Specifically, the ejector 81 has a nozzle portion 811 that injects a fluid, a suction portion 812 that sucks the fluid from the outlet side of the fuel cell 10, and a discharge portion 813 that mixes the fluid injected from the nozzle portion 811 with the fluid sucked from the suction portion 812 and discharges the mixture toward the reformer 33.

[0163] The nozzle portion 811 has a throttle structure capable of injecting a fluid. The nozzle portion 811 is configured with a fixed throttle structure in which the throttle opening is fixed. In addition, the discharge portion 813 has a flow path cross-sectional area that expands toward the downstream side so that the fluid from the nozzle portion 811 and the fluid from the suction portion 812 are mixed and then pressurized. Note that the nozzle portion 811 may be configured with a variable throttle structure in which the throttle opening is variable.

[0164] The suction section 812 of the ejector 81 is configured to suck fluid from the outlet side of the fuel cell 10 by utilizing the negative pressure on the outlet side of the nozzle section 811. Specifically, the suction section 812 is connected to an off-gas circulation flow path 80 branching off from the fuel discharge pipe 52 so that a portion of the fuel off-gas discharged from the fuel outlet section 10d of the fuel cell 10 is sucked in.

[0165] Here, the ejector 81 has a characteristic that the flow rate of the suction fluid sucked from the suction portion 812 increases as the mass flow rate of the fluid flowing into the nozzle portion 811 as the driving flow increases. Therefore, by increasing the mass flow rate of the fuel gas flowing into the nozzle portion 811 of the ejector 81, it is possible to increase the suction flow rate of the fuel off-gas sucked from the suction portion 812.

[0166] For example, when the circulation gas adjustment valve 42 is opened to increase the flow rate of the circulation gas flowing through the fuel circulation flow path 40, the flow rate of the fuel gas flowing through the fuel supply flow path 30 increases, and therefore the flow rate of the driving flow of the ejector 81 can be increased. This increases the suction flow rate of the fuel off-gas sucked through the suction part 812. In other words, by increasing the valve opening of the circulation gas adjustment valve 42 to increase the flow rate of the recycled gas, the amount of fuel gas supplied to the reformer 33 can be increased without increasing the amount of fuel supplied from outside the fuel cell system 1.

[0167] Furthermore, when the circulation gas regulating valve 42 is opened to increase the flow rate of the circulation gas flowing through the fuel circulation flow path 40, the circulation gas temperature Ta drops compared to before the circulation gas flow rate was increased. The control device 100 executes the control processing of steps S10 to S70 described in the first embodiment based on the circulation gas temperature Ta when the circulation gas regulating valve 42 is open, which is obtained from the detection signal sent from the circulation gas temperature detection unit 43. That is, the control device 100 changes the rotation speed of the blower fan 70a based on the circulation gas temperature Ta, which changes depending on the circulation gas flow rate that changes due to the operation of the circulation gas regulating valve 42.

[0168] The control device 100 may adjust the valve opening of the circulation gas adjustment valve 42 based on a detection signal transmitted from the recycling flow rate detection unit 82 according to the flow rate of the recycling gas.

[0169] According to this, by adjusting the valve opening of the circulation gas regulating valve 42 to increase the circulation gas flowing through the fuel circulation flow path 40, the amount of fuel gas supplied to the reformer 33 can be adjusted without increasing the amount of fuel supplied from outside the fuel cell system 1.

[0170] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0171] In the above-described embodiment, an example has been described in which the blower 70 is disposed upstream of the first heat exchanger 41 in the air flow direction, but the present invention is not limited to this. For example, the blower 70 may be disposed downstream of the first heat exchanger 41 in the air flow direction.

[0172] In the above embodiment, the control device 100 reduces the rotation speed of the blower fan 70a when the exhaust gas temperature To is lower than the cooling judgment temperature so that the exhaust gas temperature To approaches the cooling judgment temperature. However, the present invention is not limited to this. For example, the control device 100 may control the rotation speed of the blower fan 70a so that the exhaust gas temperature To becomes higher than the cooling judgment temperature.

[0173] In the above embodiment, the control device 100 reduces the rotation speed of the blower fan 70a when the circulating gas temperature Ta is lower than the target heating temperature so that the circulating gas temperature Ta becomes equal to or higher than the target heating temperature. However, the present invention is not limited to this. For example, the control device 100 may control the rotation speed of the blower fan 70a so that the circulating gas temperature Ta becomes lower than the target heating temperature.

[0174] In the above embodiment, the control device 100 reduces the rotation speed of the blower fan 70a when the circulation gas temperature Ta is lower than the condensation threshold temperature so that the circulation gas temperature Ta approaches the condensation threshold temperature. However, the present invention is not limited to this. For example, the control device 100 may control the rotation speed of the blower fan 70a so that the circulation gas temperature Ta becomes higher than the condensation threshold temperature.

[0175] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0176] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are expressly stated as being essential or are clearly limited to a specific number in principle.

[0177] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are limited in principle to specific shapes, positional relationships, etc. [Explanation of symbols]

[0178] 10 fuel cell 30 fuel supply passage 33 Reformer 40 fuel circulation channel 41 1st heat exchange section 53 Combustor 54 Exhaust gas flow path 60 Second heat exchange section 70 Blower

Claims

1. 1. A fuel cell system, comprising: a fuel cell (10) that outputs electrical energy through an electrochemical reaction between a fuel gas and an oxidant gas; a fuel supply flow path (30) for supplying the fuel gas to the fuel cell; a reformer (33) that reforms the reforming material flowing through the fuel supply passage into the fuel gas and supplies the fuel gas to the fuel cell; a fuel circulation flow path (40) that guides a portion of the fuel gas flowing from the reformer toward the fuel cell as a circulation gas to a side of the fuel supply flow path upstream of the reformer; a combustor (53) that combusts the fuel off-gas and oxidant off-gas discharged from the fuel cell to generate exhaust gas; an exhaust gas flow path (54) connected to the combustor and guiding the exhaust gas generated in the combustor to the outside of the fuel cell system; a first heat exchange section (41) that exchanges heat between the circulating gas and air to adjust the temperature of the circulating gas; a second heat exchange section (60) that adjusts the temperature of the exhaust gas by exchanging heat between the exhaust gas flowing through the exhaust gas flow path and air; a blower (70) that blows out air used for heat exchange in the first heat exchange section and the second heat exchange section, The fuel cell system, wherein the first heat exchanger and the second heat exchanger are arranged at positions where they at least partially overlap each other in an air flow direction, which is a direction in which the air blown out by the blower flows.

2. 2. The fuel cell system according to claim 1, wherein the first heat exchanger is disposed upstream of the second heat exchanger in the air flow direction.

3. 2. The fuel cell system according to claim 1, wherein the first heat exchanger is disposed downstream of the second heat exchanger in the air flow direction.

4. 2. The fuel cell system according to claim 1, wherein the blower is disposed upstream of the first heat exchanger in the air flow direction.

5. A control device (100) for controlling the operation of the blower is provided, The blower includes a blower fan (70a) that rotates to generate an air flow, 2. The fuel cell system of claim 1, wherein the control device changes the air flow direction to either a direction from the first heat exchange unit toward the second heat exchange unit or a direction from the second heat exchange unit toward the first heat exchange unit by switching the rotation direction of the blower fan.

6. 2. The fuel cell system of claim 1, wherein the second heat exchange unit includes: a refrigerant flow path (601) through which a refrigerant having a higher heat transfer coefficient than the air blown out by the blower flows; a refrigerant circulation unit (602) for circulating the refrigerant; an exhaust heat exchanger (603) provided in the exhaust gas flow path for exchanging heat between the refrigerant and the exhaust gas flowing through the exhaust gas flow path; and a radiator (604) provided at a position overlapping with the first heat exchange unit in the air flow direction for exchanging heat between the refrigerant discharged from the exhaust heat exchanger and the air blown out by the blower.

7. the exhaust gas flow path includes an exhaust gas blowout portion (54a) that blows the exhaust gas flowing through the exhaust gas flow path to the outside of the exhaust gas flow path, 2. The fuel cell system according to claim 1, wherein the exhaust gas blow-out section is disposed downstream of the first heat exchange section and the second heat exchange section in the air flow direction.

8. an exhaust gas temperature detection unit (61) that detects the exhaust gas temperature, which is the temperature of the exhaust gas that has been heat exchanged in the second heat exchange unit; A control device (100) that controls the operation of the blower, The blower includes a blower fan (70a) that rotates to generate an air flow, 2. The fuel cell system of claim 1, wherein the control device reduces the rotation speed of the blower fan so that the exhaust gas temperature approaches the cooling judgment temperature when the exhaust gas temperature is lower than a cooling judgment temperature that determines whether the exhaust gas is at a temperature at which it can be discharged.

9. a circulation gas temperature detection unit (43) for detecting a circulation gas temperature, which is the temperature of the circulation gas that has undergone heat exchange in the first heat exchange unit; A control device (100) that controls the operation of the blower, The blower includes a blower fan (70a) that rotates to generate an air flow, 2. The fuel cell system according to claim 1, wherein, when the circulating gas temperature is lower than a target heating temperature required to heat the reformer, the control device reduces the rotation speed of the blower fan so that the circulating gas temperature becomes equal to or higher than the target heating temperature.

10. 10. The fuel cell system of claim 9, wherein the control device reduces the rotation speed of the blower fan so that the circulation gas temperature approaches the condensation judgment temperature when the circulation gas temperature is higher than the target heating temperature and lower than a condensation judgment temperature that determines whether the circulation gas is at a temperature at which it is likely to condense when the circulation gas is flowed into the fuel supply flow path.

11. an ejector (81) provided upstream of the reformer in the fuel supply flow path, the ejector having a nozzle portion (811) for injecting a fluid flowing through the fuel supply flow path as a driving flow, a suction portion (812) for sucking a fluid from a fuel outlet side of the fuel cell, and a discharge portion (813) for mixing the fluid injected from the nozzle portion with the fluid sucked from the suction portion and discharging the mixture toward the reformer; an off-gas circulation flow path (80) for guiding a portion of the fuel off-gas, including unreacted fuel gas discharged from the fuel cell, to the suction portion; a circulation gas adjusting unit (42) that adjusts the flow rate of the circulation gas flowing through the fuel circulation flow path, 11. The fuel cell system according to claim 9, wherein the control device changes the rotation speed of the blower fan based on the circulating gas temperature, which changes in accordance with the flow rate of the circulating gas, which changes due to operation of the circulating gas adjusting unit.

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