JP6377978B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As one type of fuel cell system, one shown in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, the fuel cell system includes a desulfurizer 22 for removing sulfur components in the reforming raw material supplied through the reforming raw material supply flow path 14, and desulfurization. A reformer 4 for reforming the reforming raw material, and a fuel cell stack 6 for generating electric power by oxidation and reduction of the reforming reforming raw material and the oxidizing agent. In this fuel cell system, since the desulfurization reaction of the reforming raw material by the desulfurizer 22 is performed under conditions containing hydrogen, a part of the reforming and reforming raw material reformed by the reformer 4 is desulfurized. A recycling channel 48 is provided for returning to the above. The recycle flow path 48 is provided with an orifice member 50, and the flow rate of the reforming / reforming raw material returned to the desulfurizer 22 by the orifice member 50 is adjusted.

JP 2011-159485 A

In the fuel cell system described in Patent Document 1 described above, the flow rate of the reforming / reforming raw material returned to the reformer 4 by the orifice member 50 is adjusted in the recycle channel 48, but the orifice member There is a possibility that the 50 flow path holes may be blocked by foreign matter. When the flow path hole of the orifice member 50 is blocked by a foreign substance, the reforming / reforming raw material does not flow into the recycle flow path 48, and the desulfurizer 22 does not mix the reforming / reforming raw material hydrogen, thereby desulfurizing function. There was a risk of lowering. Further, when the desulfurization function is lowered in the desulfurizer 22, the fuel cell stack 6 may be deteriorated by a sulfur component contained in the reforming / reforming raw material.
The present invention has been made to solve the above-described problems, and in a fuel cell system, an abnormality of a recycle fuel pipe for returning a part of fuel reformed in a reforming section to a desulfurizer is reliably detected. Therefore, an object is to suppress the deterioration of the reforming part and the failure of the fuel cell due to the sulfur component.

In order to solve the above problems, a fuel cell system according to claim 1 includes a fuel cell that generates electric power using a fuel containing hydrogen and an oxidant gas, an evaporation unit that generates steam from reformed water, and a reforming raw material. A reformer that generates fuel from water and steam and supplies it to the fuel cell, and uses hydrogen to remove the sulfur component contained in the reformer and supplies the reformer to the reformer A desulfurizer is connected to a fuel supply pipe that supplies fuel from the reforming unit to the fuel cell and a reforming raw material supply pipe that supplies reforming raw material to the desulfurizer, and a part of the fuel is recycled as desulfurizer Recycled fuel pipe to return to, a detection device that detects a physical quantity indicating the state of the recycled fuel flowing through the recycled fuel pipe, and detection of the passage of the recycled fuel passing through the recycled fuel pipe based on the physical quantity detected by the detection device Inspection Comprising a part, the physical quantity is a physical quantity relating to the amount of water vapor recycle fuel, the sensing device, between a connection portion of the recycled fuel tube and desulfurizer in reforming a raw material supply pipe or a distribution in the recycled fuel pipe It is installed and detects the physical quantity related to the amount of water vapor in the recycled fuel.
According to this, the passage of the recycled fuel passing through the recycled fuel pipe can be detected by the detection unit based on the physical quantity detected by the detection device. Accordingly, it is possible to reliably detect abnormality of the recycled fuel pipe. Therefore, since the recycled fuel is not supplied to the desulfurizer, it is possible to take measures so as not to cause the deterioration of the reforming section and the failure of the fuel cell due to the sulfur component not removed by the desulfurizer. As a result, in the fuel cell system, it is possible to suppress the deterioration of the reforming unit due to the sulfur component and the failure of the fuel cell.
Furthermore, the fuel and the recycled fuel that is a part of the fuel are a part of the reformed gas generated from the steam and the reforming raw material, and are a hydrogen-rich gas containing steam. Contains a large amount. Therefore, when the recycled fuel passes through the recycled fuel pipe and the reforming material supply pipe, the amount of water vapor in these pipes increases. Here, the detection device is disposed between the connection portion of the recycle fuel pipe in the reforming raw material supply pipe and the desulfurizer or in the recycle fuel pipe, and detects a physical quantity related to the water vapor amount of the recycle fuel. Therefore, the passage of the recycled fuel can be detected based on the physical quantity related to the amount of water vapor in the recycled fuel pipe and the reforming material supply pipe detected by the detection device. Here, the detection device is, for example, a humidity sensor or a dew point sensor, and is generally relatively inexpensive. Therefore, by using such a detection device, it is possible to reliably detect abnormality of the recycled fuel pipe at a relatively low cost.

The invention according to claim 2 is the fuel cell system according to claim 1 , wherein the detection device is disposed between the connection portion of the recycled fuel pipe in the reforming raw material supply pipe and the desulfurizer, The dew point sensor detects the dew point temperature of the mixed gas of raw materials and recycled fuel, the physical quantity is the dew point temperature of the mixed gas, and the fuel cell system includes a temperature sensor that detects the temperature in the reforming unit, The temperature detected by the temperature sensor and the predetermined recycling based on a map showing the relationship of the ratio of the recycled fuel to the flow rate of the recycled fuel and the dew point temperature of the mixed gas for each temperature in the reforming section A calculation unit that calculates a dew point temperature corresponding to the fuel ratio as a dew point threshold value, and the detection unit calculates the dew point temperature detected by the detection device by the calculation unit. If it is the dew point above threshold, to detect the passage of recycle fuel passing through the recycling fuel pipe.
According to this, the detection unit detects the passage of the recycled fuel passing through the recycled fuel pipe by using the dew point threshold value calculated by the calculation unit based on the dew point temperature detected by the detection device. Therefore, it is possible to accurately detect an abnormality in the recycled fuel pipe.

It is the schematic which shows the outline | summary of 1st embodiment of the fuel cell system by this invention. It is a block diagram of the fuel cell system shown in FIG. It is a flowchart of the program run with the control apparatus shown in FIG. It is a partial schematic diagram showing the outline of the first modification of the first embodiment of the fuel cell system according to the present invention. It is a flowchart of the program performed with the control apparatus in the 1st modification of 1st embodiment of the fuel cell system by this invention. It is a partial schematic diagram showing an outline of the second modification of the first embodiment of the fuel cell system according to the present invention. It is a partial schematic diagram showing an outline of a modification of the second modification of the first embodiment of the fuel cell system according to the present invention. It is a partial schematic diagram showing the outline of the third modification of the first embodiment of the fuel cell system according to the present invention. It is a figure which shows the correlation with the physical quantity which shows the state of the recycle gas detected by the detection apparatus shown in FIG. 8, and a recycle fuel ratio. It is a flowchart of the program performed with the control apparatus in the 3rd modification of 1st embodiment of the fuel cell system by this invention. It is a partial schematic diagram showing the outline of the modification of the third modification of the first embodiment of the fuel cell system according to the present invention. It is a partial schematic diagram showing an outline of the fourth modification of the first embodiment of the fuel cell system according to the present invention. It is a flowchart of the program performed with the control apparatus in the 4th modification of 1st embodiment of the fuel cell system by this invention. In each modification of 1st embodiment of the fuel cell system by this invention, it is a partial schematic diagram which shows the outline | summary at the time of arrange | positioning a pump to a recycled fuel pipe | tube. It is a block diagram of the feedback control part of the control apparatus in 2nd embodiment of the fuel cell system by this invention. It is a flowchart of the program performed with the control apparatus in 2nd embodiment of the fuel cell system by this invention.

(First embodiment)
Hereinafter, a first embodiment of a fuel cell system according to the present invention will be described. As shown in FIG. 1, the fuel cell system includes a power generation unit 10 and a hot water storage tank 21. The power generation unit 10 includes a housing 10a, a fuel cell module 11, a heat exchanger 12, an inverter device 13, a water tank 14, and a control device 15.

  As will be described later, the fuel cell module 11 includes at least a fuel cell 34. The fuel cell module 11 is supplied with reforming raw material, reforming water, and cathode air. Specifically, the fuel cell module 11 has one end connected to the supply source Gs and the other end of the reforming material supply pipe 11a to which the reforming material is supplied. Furthermore, the fuel cell module 11 has one end connected to the water tank 14 and the other end of the water supply pipe 11b to which the reforming water is supplied. The water supply pipe 11b is provided with a reforming water pump 11b1. Further, the fuel cell module 11 has one end connected to the cathode air blower 11c1 and the other end of the cathode air supply pipe 11c to which the cathode air is supplied.

  The reforming raw material supply pipe 11a will be described in detail. In the reforming material supply pipe 11a, a shutoff valve 11a1, a first pressure sensor 11a2, a flow rate sensor 11a3 (corresponding to a flow rate detection device in claims), a pressure adjustment device 11a4, and a material pump 11a5 (patent) And a desulfurizer 11a6. The shut-off valve 11a1, the first pressure sensor 11a2, the flow rate sensor 11a3, the pressure regulator 11a4, the raw material pump 11a5 and the desulfurizer 11a6 are housed in the housing 10a.

  The shut-off valve 11a1 is a valve (double valve) that shuts off the reforming raw material supply pipe 11a in accordance with a command from the control device 15 so as to be freely opened and closed. The first pressure sensor 11a2 detects the pressure of the fuel (reforming raw material) supplied to the fuel cell 34 (especially the pressure at the place where the first pressure sensor 11a2 is installed), and the detection result is a control device. 15 is transmitted. The flow rate sensor 11 a 3 detects the flow rate of the fuel (reforming raw material) supplied to the fuel cell 34, that is, the flow rate per unit time, and transmits the detection result to the control device 15.

  The pressure adjusting device 11a4 adjusts the input fuel to a predetermined pressure and outputs it. For example, the pressure adjusting device 11a4 is configured by a zero governor that outputs input fuel at atmospheric pressure. The pressure adjusting device 11a4 is for lowering the pressure with respect to a recycle gas pipe 39 (corresponding to a recycle fuel pipe in claims) on the primary side of the raw material pump 11a5 of the reforming raw material supply pipe 11a. It is. The pressure adjustment device 11a4 makes the reforming gas (recycle gas (corresponding to the recycle fuel in the claims)) circulates through the recycle gas pipe 39 by setting the reforming material supply pipe 11a to a pressure lower than that of the recycle gas pipe 39. To do. The raw material pump 11 a 5 is a raw material supply device that supplies fuel (reforming raw material) to the fuel cell 34, and in accordance with a control command value from the control device 15, the fuel supply amount (supply flow rate (per unit time) The flow rate)) is adjusted. The raw material pump 11 a 5 is a pumping device that sucks in the raw material for reforming and pumps it to the reforming unit 33.

The desulfurizer 11a6 removes a sulfur content (for example, a sulfur compound) in the reforming raw material by using hydrogen . In the desulfurizer 11a6, a catalyst and a super high-order desulfurizing agent are accommodated. In the catalyst, a sulfur compound and hydrogen react to generate hydrogen sulfide. For example, the catalyst is nickel-molybdenum or cobalt-molybdenum. As the ultra-high order desulfurizing agent, for example, a copper-zinc-based desulfurizing agent, a copper-zinc-aluminum-based desulfurizing agent, or the like can be used. The ultra-high order desulfurizing agent takes in and removes hydrogen sulfide converted from the sulfur compound by the catalyst. Such an ultra-high order desulfurization agent exhibits an excellent desulfurization action at a high temperature of 200 to 300 ° C. (for example, 250 to 300 ° C.). Therefore, the desulfurizer 11a6 is disposed at a location where the inside is in a high temperature state of 200 to 300 ° C. (for example, 250 to 300 ° C.). For example, the desulfurizer 11 a 6 is disposed in the casing 31 or on the outer surface of the casing 31.

  In the fuel cell system, a part of the reformed gas reformed in the reforming unit 33 is returned to the reforming raw material supply pipe 11a in connection with the use of the super high-order desulfurizing agent as the desulfurizing agent. It is configured. Specifically, a recycle gas pipe 39 for returning the reformed gas is provided. One end of the recycle gas pipe 39 is a reformed gas supply pipe (corresponding to the fuel supply pipe in the claims) for supplying the reformed gas (corresponding to the fuel in the claims) from the reformer 33 to the fuel cell 34. 38. The other end of the recycle gas pipe 39 is located upstream of the desulfurizer 11a6 of the reforming raw material supply pipe 11a, more specifically, the portion where the raw material pump 11a5 of the reforming raw material supply pipe 11a is disposed and the pressure adjusting device 11a4. It is connected by the connection part 11a7 between these arrangement | positioning site | parts. As a result, part of the reformed gas flowing from the reforming section 33 through the reformed gas supply pipe 38 is returned to the reforming raw material supply pipe 11 a through the recycle gas pipe 39.

  In this way, when a part of the reformed gas containing hydrogen is returned to the reforming material supply pipe 11a, hydrogen in the reformed gas is mixed with the reforming material and the reforming material is supplied. It is fed to the super high-order desulfurization agent in the desulfurizer 11a6 through the pipe 11a. As a result, the sulfur compound in the reforming raw material reacts with hydrogen to generate hydrogen sulfide, and the hydrogen sulfide is removed by the superhigh-order desulfurization agent.

The recycle gas pipe 39 is provided with a first humidity sensor 39a1, an orifice 39b, and a heat exchanger (condenser) 39c.
The first humidity sensor 39a1 is a detection device that detects humidity (particularly humidity at the installation location of the first humidity sensor 39a1), which is a physical quantity related to the amount of water vapor indicating the state of the recycle gas flowing through the recycle gas pipe 39. The first humidity sensor 39a1 is configured to transmit the detection result to the control device 15. The orifice 39b is provided on the upstream side of the first humidity sensor 39a1 of the recycle gas pipe 39. A flow path hole is provided in the orifice 39b, and the flow rate of the reformed gas returned through the recycle gas pipe 39 is adjusted by the flow path hole.
The heat exchanger 39 c is provided upstream of the orifice 39 b of the recycle gas pipe 39. Reformed water supplied to the reforming unit 33 is used as a refrigerant to exchange heat with the recycle gas, and a part of the water supply pipe 11b that supplies the reformed water to the reforming unit 33 is accommodated in the heat exchanger 39c. ing. The heat of the recycle gas is exchanged with the reformed water passing through the water supply pipe 11b.

  The heat exchanger 12 is a heat exchanger in which combustion exhaust gas exhausted from the fuel cell module 11 is supplied and hot water stored in the hot water storage tank 21 is supplied to exchange heat between the combustion exhaust gas and hot water. Specifically, the hot water storage tank 21 stores hot water, and is connected to a hot water circulation line 22 through which the hot water circulates (circulates in the direction of the arrow in the figure). On the hot water circulation line 22, a hot water circulation pump 22 a and the heat exchanger 12 are arranged in order from the lower end to the upper end of the hot water tank 21. The heat exchanger 12 is connected (penetrated) with an exhaust pipe 11 d from the fuel cell module 11. The heat exchanger 12 is connected to a condensed water supply pipe 12 a connected to the water tank 14.

  In the heat exchanger 12, the combustion exhaust gas from the fuel cell module 11 is introduced into the heat exchanger 12 through the exhaust pipe 11d, exchanged with the hot water, condensed and cooled. The condensed combustion exhaust gas is discharged to the outside through the exhaust pipe 11d. Moreover, the condensed condensed water is supplied to the water tank 14 through the condensed water supply pipe 12a. The water tank 14 purifies the condensed water with ion exchange resin.

  The heat exchanger 12, the hot water tank 21, and the hot water circulation line 22 described above constitute an exhaust heat recovery system 20. The exhaust heat recovery system 20 recovers and stores the exhaust heat of the fuel cell module 11 in hot water storage.

  Further, the inverter device 13 receives the DC voltage output from the fuel cell 34, converts it to a predetermined AC voltage, and is connected to an AC system power supply 16a and an external power load 16c (for example, an electrical appliance). To 16b. Further, the inverter device 13 receives an AC voltage from the system power supply 16 a via the power supply line 16 b, converts it to a predetermined DC voltage, and outputs it to the auxiliary machines (each pump, blower, etc.) and the control device 15. The control device 15 controls the operation of the fuel cell system by driving an auxiliary machine.

  The fuel cell module 11 (30) includes a casing 31, an evaporation unit 32, a reforming unit 33, and a fuel cell 34. The casing 31 is formed in a box shape with a heat insulating material.

  The evaporating unit 32 is heated by a combustion gas to be described later, evaporates the supplied reforming water to generate water vapor, and preheats the supplied reforming raw material. The evaporation section 32 mixes the steam generated in this way and the preheated reforming raw material and supplies the mixture to the reforming section 33. The reforming raw materials include gas fuels for reforming such as natural gas and LP gas, and liquid fuels for reforming such as kerosene, gasoline, and methanol. In this embodiment, natural gas will be described.

  The other end of the water supply pipe 11 b whose one end (lower end) is connected to the water tank 14 is connected to the evaporation unit 32. The evaporating section 32 is connected to a reforming material supply pipe 11a having one end connected to the supply source Gs. The supply source Gs is, for example, a gas supply pipe for city gas or a gas cylinder for LP gas.

  The reforming unit 33 is heated by the combustion gas described above and supplied with heat necessary for the steam reforming reaction, so that the reformed gas is generated from the mixed gas (reforming raw material, steam) supplied from the evaporation unit 32. Is generated and derived. The reforming unit 33 is filled with a catalyst (for example, Ru or Ni-based catalyst), and the mixed gas reacts with the catalyst to be reformed to generate a gas containing hydrogen gas and carbon monoxide. (So-called steam reforming reaction). The reformed gas contains hydrogen, carbon monoxide, carbon dioxide, steam, unreformed natural gas (methane gas), and reformed water (steam) that has not been used for reforming. As described above, the reforming unit 33 generates reformed gas (fuel) from the reforming raw material (raw fuel) and the reformed water and supplies the reformed gas (fuel) to the fuel cell 34. The steam reforming reaction is an endothermic reaction.

  The fuel cell 34 generates power using fuel and oxidant gas. The fuel cell 34 is configured by laminating a fuel electrode, an air electrode (oxidant electrode), and a plurality of cells 34a made of an electrolyte interposed between the two electrodes. The fuel cell of this embodiment is a solid oxide fuel cell, and uses zirconium oxide, which is a kind of solid oxide, as an electrolyte. Hydrogen, carbon monoxide, methane gas, etc. are supplied to the fuel electrode of the fuel cell 34 as fuel.

  On the fuel electrode side of the cell 34a, a fuel flow path 34b through which the reformed gas as the fuel flows is formed. An air flow path 34c through which air (cathode air) that is an oxidant gas flows is formed on the air electrode side of the cell 34a. The fuel cell 34 generates electricity using fuel and oxidant gas.

  The fuel cell 34 is provided on the manifold 35. The reformed gas from the reforming unit 33 is supplied to the manifold 35 via the reformed gas supply pipe 38. The lower end (one end) of the fuel flow path 34b is connected to the fuel outlet of the manifold 35, and the reformed gas led out from the fuel outlet is introduced from the lower end and led out from the upper end. . The cathode air sent out by the cathode air blower 11c1 is supplied via the cathode air supply pipe 11c, introduced from the lower end of the air flow path 34c, and led out from the upper end.

  The combustion unit 36 is provided between the fuel cell 34, the evaporation unit 32, and the reforming unit 33. The combustion unit 36 heats the reforming unit 33 by burning the anode offgas (fuel offgas) from the fuel cell 34 and the cathode offgas (oxidant offgas) from the fuel cell 34. In the combustion unit 36, the anode off gas is burned and a flame 37 is generated. In the combustion section 36, the anode off gas is burned and the combustion exhaust gas is generated.

  The fuel cell system further includes a control device 15. The control device 15 is connected to the first pressure sensor 11a2, the flow rate sensor 11a3, the first humidity sensor 39a1, the shutoff valve 11a1, the pumps 11a5, 11b1, 22a, and the cathode air blower 11c1 (see FIG. 2). The control device 15 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. The CPU executes various programs necessary for the operation of the fuel cell system. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Next, the operation of the fuel cell system of the first embodiment described above will be described. The control device 15 executes a program according to the flowchart shown in FIG. 3 during operation of the fuel cell system (during warm-up operation and during power generation operation). In step S102, the control device 15 acquires the detected humidity Hk of the recycled gas detected by the first humidity sensor 39a1.

  When the recycled gas passes through the recycled gas pipe 39, the first humidity sensor 39a1 detects the humidity of the recycled gas. Since the recycle gas is a part of the reformed gas reformed by the reforming unit 33, the recycle gas has a relatively high temperature and contains a large amount of water vapor. Here, since the first humidity sensor 39a1 is disposed downstream of the heat exchanger 39c, the first humidity sensor 39a1 detects the humidity of the recycled gas after being condensed by the heat exchanger 39c. The humidity of the recycled gas after condensation is approximately 100%. Therefore, in this case, the detected humidity Hk detected by the first humidity sensor 39a1 is approximately 100%.

  On the other hand, when the recycle gas does not pass through the recycle gas pipe 39, the first humidity sensor 39a1 detects the humidity of the fluid at the disposed position. When the recycle gas does not pass, the water vapor contained in the recycle gas does not pass, so the amount of water vapor contained in the fluid in the recycle gas pipe 39 is relatively small. Therefore, the humidity in the recycle gas pipe 39 is relatively low. In this case, the humidity of the fluid in the recycle gas pipe 39 is specifically confirmed to be about 20% or less in advance by actual measurement by experiments or the like. Therefore, in this case, the detected humidity Hk detected by the first humidity sensor 39a1 is approximately 20% or less.

  In step S104 (detection unit), the control device 15 confirms whether or not the detected humidity Hk is equal to or higher than the humidity threshold value Hd. The humidity threshold value Hd is a threshold value for determining whether or not the recycle gas passes through the recycle gas pipe 39. Specifically, the humidity threshold Hd is a humidity between the detected humidity Hk when the recycle gas measured in advance through experiments or the like passes and the detected humidity Hk when the recycle gas does not pass. Is set to Specifically, the humidity threshold value Hd is, for example, 70%.

  When an abnormality occurs in which the flow path hole of the orifice 39b of the recycle gas pipe 39 is blocked, the recycle gas does not pass through the recycle gas pipe 39. Therefore, the detected humidity Hk detected by the first humidity sensor 39a1 is the humidity threshold. It becomes lower than the value Hd. In this case, the control device 15 determines “NO” in step S104, and detects in step S106 that an abnormality has occurred in the recycle gas pipe 39 due to the recycle gas pipe 39 being closed or the like. At this time, the control device 15 gives a warning to the user, for example. And the control apparatus 15 advances a program to step S108, and once complete | finishes it.

  On the other hand, if the recycle gas pipe 39 is normal, the recycle gas passes through the recycle gas pipe 39, so that the water vapor of the recycle gas passes. Therefore, the detected humidity Hk detected by the first humidity sensor 39a1 is the humidity. It becomes more than the threshold value Hd. In this case, the control device 15 determines “YES” in step S104, advances the program to step S108, and temporarily ends the program.

As described above, the fuel cell system according to the first embodiment includes the first humidity sensor 39a1 that is disposed in the recycle gas pipe 39 and detects humidity that is a physical quantity related to the water vapor amount of the recycle gas that passes through the recycle gas pipe 39. A detection unit (step S104) for detecting that the recycle gas passing through the recycle gas pipe 39 is normally passing based on the detected humidity Hk detected by the first humidity sensor 39a1. Therefore, the passage of the recycle gas that passes through the recycle gas pipe 39 can be detected by the detection unit (step S104) based on the humidity detected by the first humidity sensor 39a1. Thereby, the abnormality of the recycle gas pipe 39 can be reliably detected. Therefore, since the recycle gas is not supplied to the desulfurizer 11a6, it is possible to take measures to prevent the deterioration of the reforming unit 33 and the failure of the fuel cell 34 due to the sulfur component not removed by the desulfurizer 11a6. . As a result, in the fuel cell system, it is possible to suppress the deterioration of the reforming unit 33 and the failure of the fuel cell 34 due to the sulfur component.
In addition, the first humidity sensor 39a1 is generally relatively low cost, and is low in cost compared to, for example, a sensor that detects hydrogen and carbon monoxide contained in the reformed gas. Therefore, the control device 15 uses the first humidity sensor 39a1 to determine whether or not the recycle gas is normally passing through the recycle gas pipe 39 by the detection unit, thereby relatively detecting an abnormality in the recycle gas pipe 39. Detection is possible at low cost.

(First modification of the first embodiment)
Next, the first modification of the first embodiment will be described mainly with respect to differences from the first embodiment. The first modification includes a first dew point sensor 39d1 as shown in FIG. 4 in place of the first humidity sensor 39a1 provided in the fuel cell system of the first embodiment. The first dew point sensor 39d1 is a detection device that is disposed in the recycle gas pipe 39 and detects a dew point temperature that is a physical quantity related to water vapor indicating the state of the recycle gas passing through the recycle gas pipe 39. The first dew point sensor 39d1 is, for example, a capacitance type dew point sensor in which aluminum oxide is used as a sensor material. In addition, the first modification does not include the heat exchanger 39c included in the fuel cell system according to the first embodiment.

  In the first embodiment, the control device 15 executes a program according to the flowchart shown in FIG. 3, but in the first modification, the control device 15 executes a program according to the flowchart shown in FIG. . In step S202, the control device 15 acquires the detected dew point temperature Rk of the recycled gas detected by the first dew point sensor 39d1.

  When the recycled gas passes through the recycled gas pipe 39, the first dew point sensor 39d1 detects the dew point temperature of the recycled gas. In this case, the dew point temperature of the recycled gas is specifically confirmed to be about 50 ° C. or more in advance by actual measurement through experiments or the like. Therefore, in this case, the detected dew point temperature Rk detected by the first dew point sensor 39d1 is approximately 50 ° C. or higher.

  On the other hand, when the recycle gas does not pass through the recycle gas pipe 39, the first dew point sensor 39d1 detects the dew point temperature of the fluid at the disposed position. When the recycle gas does not pass, the water vapor contained in the recycle gas does not pass, so the amount of water vapor contained in the fluid in the recycle gas pipe 39 is relatively small. In this case, the dew point temperature of the fluid in the recycle gas pipe 39 is specifically confirmed to be about 10 ° C. or less in advance by actual measurement by experiments or the like. Therefore, in this case, the detected dew point temperature Rk detected by the first dew point sensor 39d1 is approximately 10 ° C. or lower.

  Then, in step S204 (detection unit), the control device 15 confirms whether or not the detected dew point temperature Rk is equal to or higher than the first dew point threshold value Rd1. The first dew point threshold value Rd1 is a threshold value for determining whether or not the recycle gas passes through the recycle gas pipe 39. Specifically, the first dew point threshold value Rd1 is a detected dew point temperature Rk when the recycle gas measured in advance through experiments or the like passes, and a detected dew point temperature Rk when the recycle gas does not pass. The dew point temperature is set between. Specifically, the first dew point threshold value Rd1 is set to 40 ° C., for example.

  When an abnormality occurs in which the flow path hole of the orifice 39b of the recycle gas pipe 39 is blocked, the recycle gas does not pass through the recycle gas pipe 39. Therefore, the detected dew point temperature Rk detected by the first dew point sensor 39d1 is the first dew point temperature Rk. It becomes lower than the dew point threshold value Rd1. In this case, the control device 15 determines “NO” in step S204. The subsequent steps are the same as those in the first embodiment described above.

  On the other hand, if the recycle gas pipe 39 is normal, the recycle gas passes through the recycle gas pipe 39, so that the detected dew point temperature Rk detected by the first dew point sensor 39d1 is equal to or higher than the first dew point threshold value Rd1. . In this case, the control device 15 determines “YES” in step S204, advances the program to step S108, and temporarily ends the program.

As described above, the fuel cell system according to the first modified example is arranged in the recycle gas pipe 39, and the first dew point sensor 39d1 that detects the dew point temperature, which is a physical quantity related to the water vapor amount of the recycle gas passing through the recycle gas pipe 39. And a detection unit (step S204) for detecting that the recycle gas passing through the recycle gas pipe 39 normally passes based on the dew point temperature Rk detected by the first dew point sensor 39d1. Thereby, the effect | action and effect similar to 1st embodiment can be acquired.
In addition, the first dew point sensor 39d1 is generally relatively low cost, and is lower in cost than a sensor that detects, for example, hydrogen or carbon monoxide contained in the reformed gas. Therefore, the control device 15 uses the first dew point sensor 39d1 to determine whether or not the recycle gas is normally passing through the recycle gas pipe 39 by the detection unit. Detection is possible at low cost.

(Second modification of the first embodiment)
Next, with respect to the second modification example of the first embodiment, portions different from the first modification example of the first embodiment will be mainly described. This second modification includes a second dew point sensor 39d2 as shown in FIG. 6 instead of the first dew point sensor 39d1 provided in the fuel cell system of the first modification described above. The second dew point sensor 39d2 is disposed between the connecting portion 11a7 and the desulfurizer 11a6 in the reforming raw material supply pipe 11a. Therefore, in the case of the second modified example, when the recycle gas passes through the recycle gas pipe 39, the portion where the second dew point sensor 39d2 is disposed is a mixed gas of the reforming raw material and the recycle gas. Pass through. That is, the second dew point sensor 39d2 is a detection device that detects the dew point temperature R of the mixed gas.
Also in the second modified example, the program according to the flowchart shown in FIG. 5 is executed as in the first modified example described above. In step S202, the control device 15 acquires the detected dew point temperature Rk of the recycle gas detected by the second dew point sensor 39d2.

  When the recycle gas does not pass through the recycle gas pipe 39, the recycle gas does not return to the reforming material supply pipe 11a, so that only the reforming material passes through the portion where the second dew point sensor 39d2 is disposed. Here, the amount of water vapor contained in the reforming raw material is generally relatively small. Specifically, it has been confirmed beforehand by actual measurement that the dew point temperature of the reforming raw material is about minus 40 ° C. Therefore, in this case, the detected dew point temperature Rk detected by the second dew point sensor 39d2 is approximately minus 40 ° C.

On the other hand, when the recycle gas passes through the recycle gas pipe 39, the recycle gas returns to the reforming material supply pipe 11a. Therefore, the reforming material, the recycle gas, Pass through. Therefore, the second dew point sensor 39d2 detects the dew point temperature R of the mixed gas of the reforming raw material and the recycle gas as the detected dew point temperature Rk. In this case, the water vapor amount of the mixed gas of the reforming raw material and the recycle gas increases by the amount of the water vapor amount of the recycle gas as compared with the case where only the reforming raw material passes. In this case, the dew point temperature R of the mixed gas varies depending on the flow rate of the recycle gas necessary for desulfurizing the reforming raw material. Specifically, it is about 40 ° C. or more by actual measurement by experiments or the like in advance. It has been confirmed. Therefore, in this case, the detected dew point temperature Rk detected by the second dew point sensor 39d2 is approximately 40 ° C. or higher.
Here, the first dew point threshold value Rd1 is a value between the detected dew point temperature Rk when the recycled gas measured in advance through experiments or the like passes and the detected dew point temperature Rk when the recycled gas does not pass. The dew point temperature is set. In the second modification, the first dew point threshold value Rd1 is set to 10 ° C., for example.

  As described above, the fuel cell system according to the second modification is disposed between the connection portion 11a7 of the recycle gas pipe 39 and the desulfurizer 11a6 in the reforming raw material supply pipe 11a and passes through the recycle gas pipe 39. A second dew point sensor 39d2 for detecting the dew point temperature R of the mixed gas of the reforming raw material and the recycle gas as a physical quantity related to the water vapor amount of the recycle gas, and a recycle gas pipe based on the detected dew point temperature Rk of the second dew point sensor 39d2. And a detection unit (step S204) for detecting that the recycle gas passing through 39 normally passes through. Thereby, the effect | action and effect similar to the 1st embodiment and the 1st modification of 1st embodiment can be acquired.

Here, a modification of the second modification will be described. The fuel cell system of the second modified example includes the second dew point sensor 39d2, but instead detects the humidity, which is a physical quantity related to the amount of water vapor indicating the state of the recycled gas, as shown in FIG. A second humidity sensor 39a2 is provided. In this case, when the recycle gas passes through the recycle gas pipe 39, the mixed gas of the reforming raw material and the recycle gas passes through the portion where the second humidity sensor 39a2 is disposed. That is, the second humidity sensor 39a2 is a detection device that detects the humidity of the mixed gas.
In the second modification, the control device 15 executes the program according to the flowchart shown in FIG. 5, but instead executes the program according to the flowchart shown in FIG. In step S102, the control device 15 acquires the detected humidity Hk of the mixed gas detected by the second humidity sensor 39a2.

When the recycle gas does not pass through the recycle gas pipe 39, the recycle gas does not return to the reforming material supply pipe 11a, so that only the reforming material passes through the portion where the second humidity sensor 39a2 is disposed. In this case, the second humidity sensor 39a2 detects the humidity of only the reforming raw material as the detected humidity Hk.
On the other hand, when the recycle gas passes through the recycle gas pipe 39, the recycle gas returns to the reforming material supply pipe 11a. Therefore, the reforming material, the recycle gas, Pass through. In this case, the second humidity sensor 39a2 detects the humidity of the mixed gas of the reforming raw material and the recycled gas as the detected humidity Hk.
In this case, the water vapor amount of the mixed gas of the reforming raw material and the recycle gas is increased as compared with the case where only the reforming raw material passes by the amount of the recycle gas water vapor. Accordingly, the detected humidity Hk detected by the second humidity sensor 39a2 when the recycled gas passes through the recycled gas pipe 39 is higher than when the recycled gas does not pass through the recycled gas pipe 39. By setting the humidity threshold value Hd based on this difference, it is possible to detect the passage of the recycle gas passing through the recycle gas pipe 39.

(Third modification of the first embodiment)
Next, regarding the third modified example of the first embodiment, portions different from the second modified example of the first embodiment will be mainly described. As shown in FIG. 8, the fuel cell system of the third modification further includes a first temperature sensor 33a (corresponding to a temperature sensor in the claims) that detects the temperature in the reforming unit 33. Further, the control device 15 stores a map M. As shown in FIG. 9, the map M is a recycle gas ratio (= recycle gas flow rate / reformer raw material flow rate; a recycle fuel ratio in the claims) indicating a ratio of a recycle gas flow rate to a reforming material flow rate. Equivalent) Rp and the dew point temperature R of the mixed gas represent the correlation for each temperature Th in the reforming section 33. This correlation is derived by being measured in advance through experiments or the like. In FIG. 8, the temperature Th increases in the order of the first temperature Th1, the second temperature Th2, and the third temperature Th3 in the temperature Th in the reforming unit 33. That is, when compared with the same recycle gas ratio Rp, the dew point temperature R of the mixed gas is lower when the temperature Th in the reforming section 33 is higher.

  In the second modification described above, the control device 15 executes a program according to the flowchart shown in FIG. 5, but in the third modification, the control device 15 follows the flowchart shown in FIG. Run the program. In step S302, the control device 15 acquires the detected temperature Thk in the reforming unit 33 detected by the first temperature sensor 33a, and advances the program to step S304.

In step S304 (calculation unit), the control device 15 calculates the second dew point threshold value Rd2 from the detected temperature Thk and the predetermined recycle gas ratio (corresponding to the predetermined recycle fuel ratio in the claims) Rps based on the map M. (Corresponding to the dew point threshold value in the claims) is calculated. The predetermined recycle gas ratio Rps is a value stored in the control device 15 in advance. Specifically, the predetermined recycle gas ratio Rps is the recycle gas ratio Rp in which the flow rate of the recycle gas including the hydrogen amount necessary for removing the sulfur component contained in the reforming raw material is secured. Here, for example, when the detected temperature Thk is the second temperature Th2, as shown in FIG. 9, based on the correlation of the second temperature Th2, the predetermined dew point temperature of the mixed gas corresponding to the predetermined recycle gas ratio Rps Rs is calculated as the second dew point threshold value Rd2.
In step S306, the control device 15 acquires the detected dew point temperature Rk detected by the second dew point sensor 39d2, and advances the program to step S308.

  In step S308 (detection unit), the control device 15 confirms whether or not the detected dew point temperature Rk is equal to or higher than the second dew point threshold value Rd2. For example, when an abnormality occurs in which the flow path hole of the orifice 39b is close to the closed state, the flow rate of the recycle gas passing through the recycle gas pipe 39 is decreased, so that the detected dew point temperature Rk is greater than the second dew point threshold value Rd2. When it becomes small, the control apparatus 15 determines with "NO" in step S308. Then, in step S106, the control device 15 determines that the flow rate of the recycle gas necessary for desulfurization of the reforming raw material is not ensured, for example, because the flow path hole of the orifice 39b is close to the closed state. The abnormality of the recycle gas pipe 39 is detected.

  On the other hand, when the flow rate of the recycle gas passing through the recycle gas pipe 39 secures a flow rate necessary for desulfurization of the reforming raw material, the detected dew point temperature Rk detected by the second dew point sensor 39d2 is It becomes 2nd dew point threshold value Rd2 or more. In this case, the control device 15 determines “YES” in step S308, advances the program to step S108, and temporarily ends the program.

Thus, the detection device is disposed between the connection portion 11a7 of the recycle gas pipe 39 in the reforming raw material supply pipe 11a and the desulfurizer 11a6, and the dew point temperature of the mixed gas of the reforming raw material and the recycle gas. The dew point sensor 39d2 that detects R, the physical quantity is the dew point temperature R of the mixed gas, and the fuel cell system further includes a first temperature sensor 33a that detects the temperature Th in the reforming unit 33. . The control device 15 creates a map M representing the relationship between the recycle gas ratio Rp indicating the ratio of the flow rate of the recycle gas to the flow rate of the reforming raw material and the dew point temperature R of the mixed gas for each temperature Th in the reforming unit 33. Based on the detected temperature Thk detected by the first temperature sensor 33a and the predetermined dew point temperature Rs corresponding to the predetermined recycle gas ratio Rps, a calculating unit (step S304) is further provided. ing. When the detected dew point temperature Rk detected by the second dew point sensor 39d2 is equal to or higher than the second dew point threshold value Rd2 calculated by the calculating unit, the detection unit (step S308) uses the recycle gas that passes through the recycle gas pipe 39. Detect the passage of.
According to this, the detection unit uses the second dew point threshold value Rd2 calculated by the calculation unit based on the dew point temperature R of the mixed gas detected by the second dew point sensor 39d2, thereby using the recycle gas pipe 39. It is possible to detect the passage of the recycle gas passing through. Therefore, the abnormality of the recycle gas pipe 39 can be detected with high accuracy.
In the third modification, the predetermined recycle gas ratio Rps is a recycle gas ratio Rp in which the flow rate of the recycle gas including the hydrogen amount necessary for removing the sulfur component contained in the reforming raw material is secured. However, instead of this, the predetermined recycle gas ratio Rps is set to be larger than zero and smaller than the recycle gas ratio Rp for which the flow rate of the recycle gas necessary for desulfurization of the reforming raw material is not secured. Also good. According to this, the control device 15 can determine whether or not the recycle gas passes through the recycle gas pipe 39 by the detection unit.
In the third modification, the predetermined recycle gas ratio Rps is a constant value, but instead, for example, it may be changed according to the flow rate of the reforming raw material.

Further, in the third modification, the fuel cell system includes the second dew point sensor 39d2, but instead of this, as shown in FIG. 11, the recycle gas pipe 39 in the reforming material supply pipe 11a is provided. You may make it further provide the 3rd humidity sensor 39a3 arrange | positioned between the connection part 11a7 and the desulfurizer 11a6, and the 2nd temperature sensor 11a8. The third humidity sensor 39a3 is a detection device that detects the humidity of the mixed gas. The second temperature sensor 11a8 is a detection device that detects the temperature of the mixed gas. Accordingly, the dew point temperature R of the mixed gas can be calculated from the detected value of the second temperature sensor 11a8 and the detected humidity Hk detected by the third humidity sensor 39a3. According to this, based on the correlation between the dew point temperature R of the mixed gas and the recycle gas ratio Rp shown in FIG. Rd2 can be set. Therefore, when the flow rate of the recycle gas passing through the recycle gas pipe 39 is reduced and the raw material for reforming is not sufficiently desulfurized, the control device 15 causes the detection unit (step S308) to Abnormality can be detected.
When the fuel cell system includes a temperature sensor that detects the temperature in the housing 10a and the temperature detected by the temperature sensor can be regarded as the temperature of the mixed gas, the detection result of the temperature sensor The dew point temperature R of the mixed gas may be calculated based on the detection result of the third humidity sensor 39a3. In this case, the second temperature sensor 11a8 can be omitted.

(Fourth modification of the first embodiment)
Next, a fourth modification of the first embodiment will be described mainly regarding the differences from the first embodiment. In the fourth modified example, instead of the first humidity sensor 39a1 provided in the fuel cell system of the first embodiment, as shown in FIG. 12, a second pressure sensor 39e (corresponding to the pressure sensor in the claims) is used. ). The second pressure sensor 39 e is a detection device that is disposed in the recycle gas pipe 39 and detects a pressure that is a physical quantity indicating the state of the recycle gas passing through the recycle gas pipe 39.

In the first embodiment, the control device 15 executes a program according to the flowchart shown in FIG. 3, but in the fourth modification, the control device 15 executes a program according to the flowchart shown in FIG. . In step S402, the control device 15 acquires the detected pressure value Pk of the recycle gas detected by the second pressure sensor 39e.
When the recycle gas passes through the recycle gas pipe 39, the recycle gas pressure is generated because the flow rate of the recycle gas is generated. Therefore, the second pressure sensor 39e detects the pressure of the recycled gas as the detected pressure value Pk. In this case, the detected pressure value Pk of the recycle gas detected by the second pressure sensor 39e has been confirmed in advance by actual measurement through experiments or the like to be approximately 50 kPa or more.

  When the recycled gas does not pass through the recycled gas pipe 39, the flow rate of the recycled gas is zero, so that the pressure of the recycled gas does not occur. Therefore, the second pressure sensor 39e detects the pressure of the fluid at the disposed position. In this case, the detected pressure value Pk of the recycle gas detected by the second pressure sensor 39e has been confirmed in advance by actual measurement through experiments or the like to be about 5 kPa or less.

  Then, in step S404 (detection unit), the control device 15 confirms whether or not the detected pressure value Pk is equal to or greater than the pressure threshold value Pd. The pressure threshold value Pd is a threshold value for determining whether or not the recycle gas passes through the recycle gas pipe 39. Specifically, the pressure threshold value Pd is between the detected pressure value Pk when the recycle gas measured in advance through experiments or the like passes and the detected pressure value Pk when the recycle gas does not pass. The pressure value is set. Specifically, the pressure threshold value Pd is set to 30 kPa, for example.

  When an abnormality occurs in which the flow path hole of the orifice 39b of the recycle gas pipe 39 is blocked, the recycle gas does not pass through the recycle gas pipe 39, so that the detected pressure value Pk detected by the second pressure sensor 39e is increased. It becomes lower than the threshold value Pd. In this case, the control device 15 determines “NO” in step S404. The subsequent steps are the same as those in the first embodiment described above.

  On the other hand, if the recycle gas pipe 39 is normal, the recycle gas passes through the recycle gas pipe 39, so that the detected pressure value Pk detected by the second pressure sensor 39e is equal to or greater than the pressure threshold value Pd. In this case, the control device 15 determines “YES” in step S404, advances the program to step S108, and temporarily ends the program.

As described above, the fuel cell system of the fourth modified example is provided with the second pressure sensor 39e that is disposed in the recycle gas pipe 39 and detects a pressure that is a physical quantity indicating the state of the recycle gas that passes through the recycle gas pipe 39. And a detection unit (step S404) for detecting that the recycle gas passing through the recycle gas pipe 39 normally passes based on the detected pressure value Pk of the second pressure sensor 39e. Thereby, the effect | action and effect similar to 1st embodiment can be acquired.
Further, the second pressure sensor 39e is generally relatively low cost, and is low in cost as compared with, for example, a sensor that detects hydrogen and carbon monoxide contained in the reformed gas. Therefore, the control device 15 uses the second pressure sensor 39e to determine whether or not the recycle gas pipe 39 is normally passing through the recycle gas pipe 39 by using the detection unit, thereby relatively detecting an abnormality in the recycle gas pipe 39. Detection is possible at low cost.

In the fourth modification, the second pressure sensor 39e is disposed in the recycle gas pipe 39. Instead, the second pressure sensor 39e is connected to the connection portion 11a7 of the recycle gas pipe 39 in the reforming material supply pipe 11a. You may make it arrange | position between desulfurizers 11a6. In this case, when the recycle gas passes through the recycle gas pipe 39, the mixed gas of the reforming raw material and the recycle gas passes through the portion where the second pressure sensor 39e is disposed. That is, the second pressure sensor 39e detects the pressure of the mixed gas.
In this case, the flow rate of the mixed gas of the reforming material and the recycle gas that passes through the reforming material supply pipe 11a is larger than the case where only the reforming material passes by the amount of the recycle gas. Accordingly, the detected pressure value Pk detected by the second pressure sensor 39e when the recycled gas passes through the recycled gas pipe 39 is higher than when the recycled gas does not pass through the recycled gas pipe 39. By setting the pressure threshold value Pd based on this difference, it is possible to detect the passage of the recycle gas passing through the recycle gas pipe 39.

  Further, instead of the second pressure sensor 39e in the fourth modified example described above, in the recycle gas pipe 39, pressure sensors for detecting the pressure in the recycle gas pipe 39 are arranged on the upstream side and the downstream side of the orifice 39b, respectively. You may make it do. The control device 15 calculates a pressure difference between the upstream side and the downstream side of the orifice 39b from the values detected by these pressure sensors, and determines whether or not the recycle gas passes through the recycle gas pipe 39. That is, when the recycle gas passes through the recycle gas pipe 39, the pressure loss due to the orifice 39b can be detected as a pressure difference between the upstream side and the downstream side of the orifice 39b. On the other hand, when the recycle gas does not pass through the recycle gas pipe 39, pressure loss due to the orifice 39b does not occur, so that a pressure difference between the upstream side and the downstream side of the orifice 39b does not occur. Therefore, by providing the pressure threshold value Pd between the pressure difference when the recycle gas is passing and the pressure difference when the recycle gas is not passing, the control device 15 is connected to the recycle gas pipe 39. It can be determined whether or not the recycle gas is passing.

Further, in each of the above-described embodiments (variants), a pressure regulator 11a4 is provided in the reforming raw material supply pipe 11a as a recycle fuel supply apparatus for circulating the reformed gas (recycled fuel) through the recycle gas pipe 39. Instead of this, as a recycled fuel supply device for circulating reformed gas (recycled fuel) through the recycled gas pipe 39, as shown in FIG. 14, a pump 39f for sending the recycled gas to the recycled gas pipe 39 is provided. May be provided. In this case, the fuel cell system may not include the orifice 39b.
Further, in this case, the control device 15 can control the flow rate of the recycle gas passing through the recycle gas pipe 39 by the pump 39f. Therefore, in the above-described third modification, when the dew point temperature R of the mixed gas is smaller than the second dew point threshold value Rd2, that is, when the recycle gas ratio Rp is smaller than the predetermined recycle gas ratio Rps, the control device 15 controls the pump 39f. Can be increased, the flow rate of the recycle gas can be increased, and the recycle gas ratio Rp can be increased. Thereby, the recycle gas ratio Rp can be made equal to or higher than the predetermined recycle gas ratio Rps, and the flow rate of the recycle gas necessary for performing desulfurization of the reforming raw material can be ensured. Even when the pump 39f is not provided, the controller 15 controls the raw material pump 11a5 when there is a correlation between the flow rate of the reforming raw material pumped by the raw material pump 11a5 and the flow rate of the recycle gas. The flow rate of the recycle gas may be controlled according to the recycle gas ratio Rp.

(Second embodiment)
Next, the second embodiment will be described mainly with respect to differences from the first embodiment. The fuel cell system according to the second embodiment does not include the first humidity sensor 39a1 included in the fuel cell system according to the first embodiment. In the fuel cell system according to the second embodiment, the control device 15 further includes a feedback control unit 15a.

  The feedback control unit 15a calculates a control command value for the raw material pump 11a5 so that the actual flow rate Qr, which is the flow rate of the reforming raw material detected by the flow rate sensor 11a3, becomes the target flow rate Qt. This is a part that performs feedback control to be output to the pump 11a5. As shown in FIG. 15, the feedback control unit 15a includes a subtraction unit 15a1 and a control command value calculation unit 15a2. The target flow rate Qt is derived based on the power consumption of the external power load 16c and the fuel supply map stored in advance in the control device 15. The fuel supply map shows the correlation between the power consumption of the external power load 16c and each supply amount (target flow rate Qt) of the reforming raw material, reforming water, and cathode air.

  The subtraction unit 15a1 receives the target flow rate Qt and the actual flow rate Qr. The subtraction unit 15a1 subtracts the actual flow rate Qr from the target flow rate Qt to calculate a deviation between both flow rates (= target flow rate Qt−actual flow rate Qr) et, and outputs the calculated value to the control command value calculation unit 15a2. The control command value calculator 15a2 calculates a control command value (rotation speed) of the material pump 11a5 based on the input deviation. Here, since the material pump 11a5 is PWM-controlled, the control command value is calculated by the duty ratio of PWM control. Then, the control command value is output to the driver circuit (not shown) of the material pump 11a5 at the duty ratio. Thereby, feedback control is performed so that the actual flow rate Qr becomes the target flow rate Qt according to the power consumption amount of the external power load 16c (load power amount of the fuel cell 34).

  In the first embodiment described above, a program according to the flowchart shown in FIG. 3 is executed. In the second embodiment, a program according to the flowchart shown in FIG. 16 is executed. In step S502, the control device 15 determines a predetermined duty ratio threshold value Dd1 based on the predetermined target flow rate Qt1 set to the target flow rate Qt of the reforming raw material. The predetermined duty ratio threshold value Dd1 is a value of the duty ratio threshold value Dd for determining whether or not the recycle gas normally passes through the recycle gas pipe 39 in step S508 described later.

In step S504, the control device 15 determines whether or not the difference between the actual flow rate Qr detected by the flow rate sensor 11a3 and the predetermined target flow rate Qt1 is equal to or less than a predetermined value Qs. The predetermined value Qs is a value for determining whether or not the actual flow rate Qr matches the target flow rate Qt. The predetermined value Qs is set to a value corresponding to, for example, 3% of the predetermined target flow rate Qt1 set to the target flow rate Qt.
When the difference between the actual flow rate Qr and the predetermined target flow rate Qt1 is larger than the predetermined value Qs, the control device 15 determines that the actual flow rate Qr does not match the predetermined target flow rate Qt1, and determines “NO” in step S504. Step S504 is repeatedly executed. On the other hand, if the difference between the actual flow rate Qr and the predetermined target flow rate Qt1 is equal to or less than the predetermined value Qs, the control device 15 determines that the actual flow rate Qr matches the predetermined target flow rate Qt1, and determines “YES” in step S504. Then, the program proceeds to step S506.

In step S506 (control command value detection unit), the control device 15 acquires the duty ratio at that time as the detected duty ratio Dk. Then, in step S508 (detection unit), the control device 15 determines whether or not the detected duty ratio Dk acquired in step S506 is greater than or equal to a predetermined duty ratio threshold value Dd1.
When the recycle gas does not pass through the recycle gas pipe 39, the fluid pumped by the material pump 11a5 is only the reforming material. In this case, since the flow rate of the reforming raw material has reached the predetermined target flow rate Qt1 at the time of determination in step S508, the detected duty ratio Dk is a duty ratio corresponding to the predetermined target flow rate Qt1.

  On the other hand, when the recycle gas passes through the recycle gas pipe 39, the fluid pumped by the raw material pump 11a5 is a mixed gas of the reforming raw material and the recycle gas. At this time, the flow rate of the mixed gas is a combined flow rate of the predetermined target flow rate Qt1 that is the flow rate of the reforming raw material and the flow rate of the recycle gas. Therefore, the detected duty ratio Dk in this case is a duty ratio corresponding to a flow rate obtained by combining the predetermined target flow rate Qt1 and the flow rate of the recycle gas. That is, the detected duty ratio Dk when the recycle gas passes through the recycle gas pipe 39 is increased by a duty ratio corresponding to the flow rate of the recycle gas as compared with the case where the recycle gas does not pass.

  The predetermined duty ratio threshold value Dd1 is set between a duty ratio corresponding to the predetermined target flow rate Qt1 and a duty ratio corresponding to the combined flow rate of the predetermined target flow rate Qt1 and the flow rate of the recycled gas. Here, the flow rate of the recycle gas has a predetermined correlation with the target flow rate Qt. The predetermined correlation is obtained by actual measurement through experiments or the like, and is stored in the control device 15 in advance. Based on this correlation, a flow rate of the recycle gas corresponding to the predetermined target flow rate Qt1 is derived, and a predetermined duty ratio threshold value Dd1 at the predetermined target flow rate Qt1 is set.

  Returning to the flowchart shown in FIG. When the recycle gas does not pass through the recycle gas pipe 39, the detected duty ratio Dk detected in step S506 is a duty ratio corresponding to the predetermined target flow rate Qt1. In this case, since detected duty ratio Dk is smaller than predetermined duty ratio threshold value Dd1, control device 15 determines “NO” in step S508, and advances the program to step S106. In step S106, the control device 15 detects an abnormality in the recycle gas pipe 39, advances the program to step S108, and ends it.

  On the other hand, when the recycle gas passes through the recycle gas pipe 39, the detected duty ratio Dk detected in step S506 is a duty ratio corresponding to a flow rate that combines the predetermined target flow rate Qt1 and the flow rate of the recycle gas. In this case, since the detected duty ratio Dk is equal to or greater than the predetermined duty ratio threshold value Dd1, the control device 15 determines “YES” in step S508, advances the program to step S108, and temporarily ends it.

Thus, the control device 15 of the fuel cell system of the second embodiment calculates the control command value for the raw material pump 11a5 so that the flow rate detected by the flow rate sensor 11a3 becomes the target flow rate Qt of the reforming raw material. The feedback control unit 15a that performs feedback control to output the control command value to the material pump 11a5, the control command value detection unit (step S506) that detects the detection duty ratio Dk, and the control command value detection unit A detection unit (step S508) that detects the passage of the recycle gas passing through the recycle gas pipe 39 based on the detection duty ratio Dk.
Thus, the control device 15 reliably detects a state where the recycle gas does not pass through the recycle gas pipe 39. Therefore, the fuel cell system can reliably detect the abnormality of the recycled gas pipe 39 at a relatively low cost without adding a sensor or the like for detecting the physical quantity of the recycled fuel.

In each of the above-described embodiments, an example of the fuel cell system is shown. However, the present invention is not limited to this, and other configurations can be adopted. For example, the fuel cell system including the heat exchanger 39c in each embodiment described above may not include the heat exchanger 39c.
In each of the embodiments described above, the recycle gas pipe 39 is connected between the pressure adjusting device 11a4 and the raw material pump 11a5 in the reforming raw material supply pipe 11a. May be connected between the raw material pump 11a5 and the desulfurizer 11a6.
The fuel cell 34 of the fuel cell system according to the above-described embodiment is a solid oxide fuel cell (SOFC). However, the present invention is not limited to this, and a solid polymer fuel cell (PEFC) is used as the fuel cell. ).

  DESCRIPTION OF SYMBOLS 11 ... Fuel cell module, 11a ... Raw material supply pipe for reforming, 11a3 ... Flow rate sensor (flow rate detection device), 11a4 ... Pressure regulator, 11a5 ... Raw material pump (raw material supply device), 11a6 ... Desulfurizer, 11a7 ... Connection part 11a8 ... second temperature sensor (detection device), 15 ... control device (detection unit, feedback control unit, control command value detection unit), 15a ... feedback control unit, 32 ... evaporation unit, 33 ... reforming unit, 33a ... 1st temperature sensor (temperature sensor), 34 ... fuel cell, 38 ... reformed gas supply pipe, 39 ... recycled gas pipe (recycled fuel pipe), 39a1 ... first humidity sensor (detection device), 39a2 ... second humidity sensor (Detection device), 39a3 ... third humidity sensor (detection device), 39b ... orifice, 39c ... heat exchanger, 39d1 ... first dew point sensor (detection device), 39d ... second dew point sensor (detection device), 39e ... second pressure sensor (pressure sensor; detection device), M ... map, Rd1 ... first dew point threshold value, Rd2 ... second dew point threshold value (dew point threshold value) ), Rp ... recycle gas ratio (recycle fuel ratio), Rps ... predetermined recycle gas ratio (predetermined recycle fuel ratio).

Claims (2)

A fuel cell that generates electricity using a fuel containing hydrogen and an oxidant gas;
An evaporation section for generating water vapor from the reformed water;
A reforming unit that generates the fuel from the reforming raw material and the steam and supplies the fuel to the fuel cell;
A desulfurizer that removes sulfur components contained in the reforming raw material by using the hydrogen and supplies the reforming raw material to the reforming unit;
A fuel supply pipe for supplying the fuel to the fuel cell from the reforming section and a reforming raw material supply pipe for supplying the reforming raw material to the desulfurizer are connected, and a part of the fuel is used as a recycled fuel. A recycled fuel pipe returned to the desulfurizer;
A detection device for detecting a physical quantity indicating a state of the recycled fuel flowing through the recycled fuel pipe;
A detection unit that detects the passage of the recycled fuel that passes through the recycled fuel pipe based on the physical quantity detected by the detection device , and
The physical quantity is a physical quantity related to a water vapor amount of the recycled fuel,
The detection device is disposed between the connection portion of the recycled fuel pipe and the desulfurizer in the reforming raw material supply pipe or in the recycled fuel pipe, and detects a physical quantity related to a water vapor amount of the recycled fuel. Fuel cell system. The detection device is disposed between a connection portion of the recycled fuel pipe in the reforming raw material supply pipe and the desulfurizer, and detects a dew point temperature of a mixed gas of the reforming raw material and the recycled fuel. Dew point sensor
The physical quantity is a dew point temperature of the mixed gas,
The fuel cell system includes:
A temperature sensor for detecting the temperature in the reforming section;
Based on the map representing the relationship of the recycled fuel ratio indicating the ratio of the flow rate of the recycled fuel to the flow rate of the reforming raw material and the dew point temperature of the mixed gas for each temperature in the reforming unit, the temperature sensor A calculation unit that calculates a dew point temperature corresponding to the detected temperature and a predetermined recycled fuel ratio as a dew point threshold, and
The detection unit detects passage of the recycled fuel that passes through the recycled fuel pipe when a dew point temperature detected by the detection device is equal to or higher than the dew point threshold calculated by the calculation unit. 1. Fuel cell system.

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