JP2013235735A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which can be operated with high efficiency.SOLUTION: In a fuel cell system 1, steam contained in an unused fuel circulating through a recycle fuel path 30 is condensed and the condensed water is stored in a condensed water tank 101. The recycle fuel from which the condensed water is recovered is supplied to the suction port side of an ejector. An electronic controller controls a pump 120 and adjusts the quantity of water being supplied from a water path 50 to the confluence 21 side of a fuel gas path 10, so as to bring a circulation rate Rclose to a target circulation rate R. Consequently, even if the production of electricity of a fuel cell module 90 is controlled by controlling the circulation amount of the fuel gas path by means of a blower 60, a high circulation rate can be maintained over the entire load range.

Description

  The present invention relates to a fuel cell system.

  Conventionally, fuel recycling has been proposed as a technique for improving the efficiency of fuel cells. Generally, the amount of fuel supplied to the fuel cell cannot be used for the power generation reaction, and a part of the fuel is released from the fuel cell as unused fuel.

  Therefore, there is a fuel that can squeeze out the fuel by recirculating unused fuel using an ejector, thereby improving power generation efficiency. The ejector mixes the unused fuel sucked from the suction port by the raw fuel gas flow injected from the nozzle portion and the raw fuel injected from the nozzle portion and discharges them to the fuel cell side. In addition, the unused fuel contains a large amount of water vapor generated by the power generation reaction, and by installing a reformer in the mixed fuel flow path, the supply of water vapor necessary for steam reforming can be supplemented by recycling.

  However, the temperature of the unused fuel is increased due to the heat generated by the fuel cell, and the temperature of the recycled fuel is high and the volume is expanded. Therefore, the suction performance of the ejector is reduced and the amount of fuel recycled cannot be increased. There was a limit to the improvement of power generation efficiency. In addition, when performing steam reforming of fuel, there is a limit to the amount of fuel that can be recycled. There was a problem of size increase and cost increase.

  In view of this, for example, Patent Document 1 proposes a fuel cell system in which the temperature of recycled fuel is lowered by a cooler to increase the amount of recycled fuel and improve power generation efficiency. In this system, the amount of water supplied from the outside can be reduced or eliminated by increasing the amount of recycling.

JP 2003-109628 A

  However, in Patent Document 1, although the amount of recycled fuel can be increased by lowering the temperature of the recycled fuel with a cooler, the mass flow ratio of the recycled fuel to the raw fuel is large. For this reason, in particular, in a low-power system of about several kW with a low raw fuel supply pressure, the required recycle fuel flow rate cannot be obtained even if the nozzle diameter of the ejector is reduced. Therefore, if the nozzle diameter of the ejector is made very small (for example, 0.3 mm or less) and the raw fuel supply pressure is greatly increased by the auxiliary machine, the recycled fuel flow rate can be obtained. This leads to a decrease in overall efficiency.

  In view of the above points, an object of the present invention is to provide a fuel cell system that can be operated with high efficiency over the entire load range.

In order to achieve the above object, in the invention according to claim 1, a reformer (80) for generating a reformed gas from a fuel gas;
A fuel cell module (90) comprising at least one fuel cell element that generates electrical energy by an electrochemical reaction between a reformed gas generated by the reformer and an oxidant;
A fuel gas flow path (10) for supplying the fuel gas to the fuel cell module side;
A condenser (100) that condenses water vapor that is not used in the electrochemical reaction and that is contained in unused fuel discharged from the fuel cell module to recover condensed water;
A recycled fuel channel (30) for returning the unused fuel from which the water vapor has been recovered by the condenser to the fuel gas channel side;
A nozzle part (71) provided in the fuel gas flow path and injecting the fuel gas, and a suction port for sucking the unused fuel from the recycled fuel flow path side by a fuel gas flow injected from the nozzle part ( 72), and an ejector (70) for mixing the fuel gas injected from the nozzle part and the unused fuel sucked from the suction port and discharging the mixed fuel to the inlet side of the fuel cell module;
A water path (50) for supplying condensed water recovered by the condenser to the upstream side of the fuel gas flow with respect to the nozzle portion of the fuel gas flow path;
A pump (120) for adjusting the amount of water supplied from the water path to the fuel gas flow path;
First detection means (151) for detecting a mass flow rate of unused fuel discharged from the fuel cell module;
Second detection means (152) for detecting a mass flow rate of unused fuel passing through the recycled fuel flow path;
The pump is controlled to supply the circulation rate, which is the ratio of the detection value of the second detection means to the detection value of the first detection means, from the water path to the fuel gas flow path side so as to approach the target value. And a control means (S120 to S160) for adjusting the amount of water to be produced.

  According to the first aspect of the present invention, the water vapor contained in the recycled fuel is condensed and recovered, and the recycled fuel recovered from the water vapor is supplied to the suction port side of the ejector. In addition, the flow of the condensed water recovered from the recycled fuel is merged with the fuel gas flow on the upstream side of the fuel gas flow with respect to the nozzle portion in the fuel gas flow path. For this reason, a high circulation rate can be maintained over the entire load range by adjusting the supply amount of the condensed water. Accordingly, it is possible to provide a fuel cell system that can be operated with high efficiency over the entire load range.

  Here, the load range is a variable range of the power generation amount of the fuel cell module. The amount of power generated by the fuel cell module varies depending on the amount of fuel gas supplied to the fuel gas flow path.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a figure which shows the structure of the fuel cell system in one Embodiment of this invention. It is a figure which shows the ejector single-piece | unit of FIG. It is a figure which shows the electrical constitution of the fuel cell system in the said embodiment. It is a flowchart which shows the control processing of the electronic control apparatus of FIG. It is a flowchart which shows the control processing of the electronic control apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of an installation type fuel cell system 1 according to the present invention.

  As shown in FIG. 1, the fuel cell system 1 of the present embodiment includes a fuel gas passage 10, a discharge passage 20, a recycled fuel passage 30, an oxidant passage 40, a water passage 50, a blower 60, an ejector 70, The reformer 80, the fuel cell module 90, the condenser 100, the pumps 110 and 120, and the combustion chamber 140 are configured.

  The fuel gas channel 10 is a channel for supplying fuel gas from a supply source of fuel gas (for example, methane) as main fuel to the fuel cell module 90 side via the reformer 80. The discharge flow path 20 is a flow path for flowing unused fuel discharged from the fuel cell module 90 to the discharge port 41 side. The recycle fuel flow path 30 is a flow path for returning unused fuel from the diversion portion 21 between the fuel cell module 90 and the discharge port to the suction port 72 (see FIG. 2) of the ejector 70. Unused fuel is fuel that has not been used for electrochemical reaction among the reformed gas output from the reformer 80.

  The oxidant channel 40 is a channel for supplying the oxidant to the fuel cell module 90. For example, air is used as the oxidizing agent in the present embodiment. The water path 50 is a flow path for supplying condensed water from the condenser 100 to the merging portion 22 in the fuel gas flow path 10. The junction 22 is located between the blower 60 and the ejector 70 in the fuel gas flow path 10.

  The blower 60 is disposed in the fuel gas flow path 10 and generates a fuel gas flow that flows toward the fuel cell module 90. An electric fan is used as the blower 60 of this embodiment.

  As shown in FIG. 1, the ejector 70 is provided between the blower 60 and the reformer 80 in the fuel gas passage 10, and returns unused fuel from the recycled fuel passage 30 to the fuel gas passage 10. It is used for. FIG. 2 is a view showing a single ejector 70. As shown in FIG. 2, the ejector 70 includes a nozzle portion 71, a suction port 72, a mixing portion 73, and a diffuser 74. The nozzle part 21 injects fuel gas. The suction port 72 sucks unused fuel from the recycled fuel channel 30 side by the fuel gas flow injected from the nozzle portion 21. The mixing unit 73 mixes the fuel gas injected from the nozzle unit 71 and the unused fuel sucked from the suction port 72 to increase the gas pressure. The diffuser 74 recovers the pressure by further reducing the gas flow rate by enlarging the passage cross-sectional area.

  The reformer 80 in FIG. 1 generates a reformed gas containing hydrogen from a fuel gas by a steam reforming reaction of a catalyst. For example, ruthenium, nickel or the like is used as the catalyst of the present embodiment.

  The fuel cell module 90 is configured by stacking a plurality of fuel cell elements. The plurality of fuel cell elements of the present embodiment are each composed of a solid oxide fuel cell (SOFC). Each of the plurality of fuel cell elements is composed of an electrolyte disposed between the anode and the cathode, and generates electric energy by an electrochemical reaction described later.

  The condenser 100 collects condensed water by cooling the water vapor contained in the unused fuel flowing in the recycled fuel flow path 30 with the oxidant in the oxidant flow path 40. Specifically, the condenser 100 includes a condensed water tank 101 and a heat exchanger 102. The condensed water tank 101 is a raw water tank that condenses water vapor contained in unused fuel flowing through the recycled fuel flow path 30 and stores condensed water. The heat exchanger 102 is provided in the oxidant channel 40 and cools and condenses unused fuel in the condensed water tank 101 with the oxidant.

  The pump 110 is provided in the oxidant flow path 40 and generates a flow of oxidant flowing toward the fuel cell module 90 side. The pump 120 is provided in the water path 50 and generates a water flow that flows from the condensed water tank 101 to the merging portion 22 side of the fuel gas passage 10. Electric pumps are used as the pumps 110 and 120 of the present embodiment, respectively.

  The combustion chamber 140 is provided on the downstream side of the discharge passage 20, and burns unused fuel in the discharge passage 20 and unused oxidant from the unused oxidant passage 45 to discharge exhaust gas from the discharge port 41. Discharge. The unused oxidant passage 45 supplies the combustion chamber 140 with an unused oxidant that has not been used in the electrochemical reaction in the fuel cell module 90 among the oxidants supplied from the oxidant flow path 40.

  Next, the electrical configuration of the fuel cell system 1 of the present embodiment will be described with reference to FIG. FIG. 3 shows an electrical configuration of the fuel cell system 1 of the present embodiment.

  The fuel cell system 1 of this embodiment includes an electronic control device 150. The electronic control device 150 includes a microcomputer, a memory, a peripheral circuit, and the like, and executes power generation control processing. The electronic control device 150 controls the blower 60, the pumps 110 and 120, and the inverter circuit 160 based on the detection values of the flow rate sensors 151 and 152 and the detection value of the residual water amount sensor 153 as the power generation control process is executed. .

  The flow sensor 151 is disposed between the fuel cell module 90 and the diversion unit 21 in the discharge channel 20 and detects the mass flow rate of unused fuel discharged from the fuel cell module 90.

  The flow rate sensor 152 is disposed between the diverter 21 and the condenser 100 in the recycled fuel flow path 30, and unused fuel flowing into the recycled fuel flow path 30 among unused fuel discharged from the fuel cell module 90. Detect the mass flow rate of the fuel.

  The remaining water amount sensor 153 detects the remaining amount of condensed water stored in the condensed water tank 101. The inverter circuit 160 converts a DC voltage generated in the fuel cell module 90 into an AC voltage and outputs the AC voltage to the electric load 170. Examples of the electric load 170 include household electric appliances.

  Next, the operation of the fuel cell system 1 of the present embodiment will be described.

  First, the electronic control unit 150 operates the blower 60 and the pumps 110 and 120, respectively.

  The blower 60 generates a flow of fuel gas that flows toward the ejector 70 in the fuel gas flow path 10. The fuel gas flowing in the fuel gas flow path 10 is mixed with water flowing from the water path 50 at the junction 22 and flows toward the inlet 71a of the ejector 70. In connection with this, the nozzle part 21 injects a fuel gas flow. The suction port 72 sucks unused fuel from the recycled fuel flow path 30 side by the fuel gas flow injected from the nozzle portion 21. In the mixing unit 73, the fuel gas injected from the nozzle unit 71 and the unused fuel sucked from the suction port 72 are mixed, and the mixed gas is blown out from the diffuser 74.

Thereafter, the reformer 80 generates a reformed gas containing hydrogen from the mixed gas blown out of the diffuser 74 by a steam reforming reaction of the catalyst. The generated reformed gas is supplied to the anodes of the plurality of fuel cell elements of the fuel cell module 90, while the oxidant (air) fed by the pump 110 is supplied to the cathodes of the plurality of fuel cell elements. Supplied from the channel 40. This causes the following electrochemical reaction to generate electrical energy.
(Cathode) 1 / 2O2 + 2e- → O ^{2-
(Anode) H2 + O 2- → H2O ++} 2e-
Water vapor is generated on the anode side by such an electrochemical reaction. The unused fuel containing water vapor flows into the discharge flow path 20 from the anodes of the plurality of fuel cell elements. A part of the unused fuel that has flowed in flows into the recycled fuel flow path 30.

  In addition, among the unused fuel that has flowed into the discharge flow path 20 from the anodes of the plurality of fuel cell elements, the remaining unused fuel other than the unused fuel that has flowed into the recycled fuel flow path 30 passes through the unused oxidant passage 45. The unused oxidant burns in the combustion chamber 140 and exhaust gas is discharged from the discharge port 41.

  On the other hand, when the unused fuel that has flowed into the recycled fuel flow path 30 from the discharge flow path 20 passes through the condensed water tank 101, it is cooled by the oxidant that passes through the heat exchanger 101. For this reason, the water vapor contained in the unused fuel is condensed and stored in the condensed water tank 101 as condensed water. That is, water vapor is recovered from unused fuel by the condenser 100. Thereafter, the unused fuel from which the water vapor has been collected flows from the recycled fuel flow path 30 to the suction port 72 of the ejector 70. Further, the condensed water stored in the condensed water tank 101 is sent to the merging portion 22 of the fuel gas flow path 10 through the water path 50 by the pump 120.

  At this time, as will be described later, the circulation rate approaches the target value by controlling the amount of water flowing from the condensed water tank 101 through the water path 50 to the merging portion 22 of the fuel gas passage 10 by the pump 120. When the mass flow rate of the unused fuel discharged from the fuel cell module 90 is Fa and the mass flow rate of the unused fuel flowing through the recycled fuel flow path 30 among the unused fuel discharged from the fuel cell module 90 is Fb, Let (Fb / Fa) × 100 be the circulation rate “%”.

  Further, when the amount of condensed water stored in the condensed water tank 101 becomes less than a predetermined amount, as will be described later, the inverter circuit 160 is controlled to increase the fuel utilization rate of the fuel cell module 90 to thereby increase the number of fuel cell elements. Increase water production in

  In the fuel cell system 1 operating in this way, the electronic control unit 150 controls the flow rate of the fuel gas flowing into the fuel gas flow path 10 by the blower 60, thereby reducing the flow rate of the reformed gas flowing into the fuel cell module 90. Can be controlled. Therefore, the electronic control unit 150 controls the blower 60 to control the flow rate of the fuel gas flow path, thereby controlling the power generation amount of the fuel cell module 90 over the entire load range from the power generation stop state to the rated power generation. be able to.

  Here, when the electronic control unit 150 controls the blower 60 and the fuel cell module 90 is performing the rated power generation operation, the fuel gas passage 10, the discharge passage 20, A recycle fuel flow path 30 and an ejector 70 are set.

Next, in the electronic control unit 160, a water supply amount control process for controlling the amount of water supplied to the fuel gas passage 10 and an inverter control process for increasing the water generation amount in the fuel cell module 90 will be described separately. To do. The electronic control device 160 executes water supply amount control processing and inverter control processing in a time-sharing manner.
(Water supply control process)
The electronic control device 160 executes water supply amount control processing according to the flowchart of FIG.

  First, in step S100, the flow rate sensor 151 detects the mass flow rate of unused fuel discharged from the fuel cell module 90 (hereinafter referred to as the discharge amount Fa). In addition, the mass flow rate (hereinafter referred to as circulation amount Fb) of the unused fuel flowing through the recycled fuel channel 30 among the unused fuel discharged from the recycled fuel channel 30 is detected by the flow sensor 152.

Next, in step S110, a circulation rate R _pv (= (Fb / Fa) × 100%) is obtained from the discharge amount Fa and the circulation amount Fb.

Next, in step S120, it is determined whether the circulation rate R _PV is less than the target circulation rate R _SET . At this time, when the circulation rate R _PV is less than the target circulation rate R _SET, it is determined as YES, and in step S130, the pump 120 is controlled to flow into the junction 22 of the fuel gas passage 10 from the water passage 50. The amount of water supplied per unit time is increased by a predetermined amount SW. As a result, the circulation rate R _PV can be increased.

Thereafter, the process returns to step S100, the discharge amount Fa is detected by the flow rate sensor 151, and the circulation amount Fb is detected by the flow rate sensor 152. In the next step S110, the circulation rate R _pv is obtained from the discharge amount Fa and the circulation amount Fb.

In the next step S120, when the circulation rate R _PV is larger than the target circulation rate R _SET , NO is determined, and YES is determined in the next step S140.

Here, too reduces the amount of water supplied to the reformer 80 and a plurality of fuel cell elements in order to reduce the circulation rate R _PV, or cause carbon precipitation by steam reaction catalyst in the reformer 80, a plurality of fuel There is a possibility that carbon deposition may occur at the anodes of the plurality of fuel cell elements due to the reaction of the battery elements.

Therefore, in the next step S150, the amount of water per unit time (W _PV −SV) obtained by subtracting the predetermined amount SV from the current water supply amount W _PV per unit time is the threshold value ST (= F _PV × S / C). It is judged whether it is larger than. The predetermined amount SV is a water reduction amount per unit time used in step S160 described later. The threshold value ST is a water supply amount per unit time at which the amount of water supplied to the reformer 80 and the plurality of fuel cell elements is insufficient and carbon deposition occurs in the reformer 80 and the plurality of fuel cell elements.

Here, the mass flow rate per time of the fuel gas to flow from the source of fuel gas by the blower 60 to the ejector 70 side and F _PV, the value set as the steam carbon ratio when the S / C, the threshold ST is F _PV × S / C. The steam carbon ratio is a molar flow rate ratio between water vapor supplied to the reformer 80 and the fuel cell module 90 and carbon based on the fuel gas (or reformed gas). S / C is a value set so as to avoid carbon deposition on the catalyst of the reformer 80 and the anodes of the plurality of fuel cell elements as the steam carbon ratio.

When the amount of water per unit time (W _PV -SV) is larger than the threshold value ST determined from such S / C and F _PV , YES is determined in step S150. If This makes it possible to determine from the current water supply quantity W _PV even if the reduced predetermined amount SV component, the carbon deposition occurs in the reformer 80 and a plurality of fuel cell elements is not a. Accordingly, in step S160, the pump 120 is controlled to reduce the amount of water supplied per unit time flowing from the water path 50 to the merging portion 22 of the fuel gas flow path 10 by a predetermined amount SV. As a result, the circulation rate R _PV can be lowered.

Thereafter, the process returns to step S100, and the discharge amount Fa is detected by the flow sensor 151. The circulation amount Fb is detected by the flow sensor 152. Thereafter, in step S110, the circulation rate R _pv is obtained from the discharge amount Fa and the circulation amount Fb. When the circulation rate R _PV is the same as the target circulation rate R _SET , NO is determined in the following steps S120 and S140, respectively. In this case, the water supply amount per unit time flowing from the water path 50 to the junction 22 of the fuel gas flow channel 10 is maintained as the current water supply amount. As a result, the circulation rate R _PV maintains the same value as the target circulation rate R _SET .

In step S150, when the amount of water (W _PV -SV) is smaller than the threshold value ST, it is determined as NO. Thus, it is determined that carbon deposition occurs in the reformer 80 and the plurality of fuel cell elements.

(Inverter control processing)
The electronic control device 160 executes inverter control processing according to the flowchart of FIG.

  First, in step S200, the remaining water amount sensor 153 detects the remaining amount of condensed water stored in the condensed water tank 101. In the next step S210, it is determined whether or not the detected remaining amount of condensed water is below a certain amount. When the detected remaining amount of condensed water is equal to or less than a predetermined amount, YES is determined in step S210. Accordingly, in step S220, the inverter circuit 160 is controlled to convert the DC voltage generated in the fuel cell module 90 into an AC voltage and output it to the electric load 170. Thus, power generation using the reformed gas is promoted in the fuel cell module 90, and the utilization rate of the fuel gas (that is, the reformed gas) can be improved.

  Accordingly, the generation of water can be increased at the anodes of the plurality of fuel cell elements of the fuel cell module 90. For this reason, the quantity of the water vapor | steam contained in the unused fuel discharged | emitted from the fuel cell module 90 to the discharge flow path 20 can be increased.

  Thereafter, in step S200, the remaining water amount sensor 153 detects the remaining amount of condensed water stored in the condensed water tank 101. In the next step S220, when the detected remaining amount of condensed water is larger than a certain amount, it is determined as NO. Accordingly, in step S230, the inverter circuit 160 is stopped. For this reason, the conversion of the DC voltage generated in the fuel cell module 90 into an AC voltage is stopped.

  According to the present embodiment described above, the water vapor contained in the unused fuel flowing through the recycled fuel flow path 30 is condensed and the condensed water is stored in the condensed water tank 101. Then, the recycled fuel from which the condensed water has been collected is supplied to the suction port side of the ejector. In addition to this, the flow of the condensed water from the condensed water tank 101 is merged with the fuel gas flow at the merge portion 22 on the upstream side of the flow of the fuel gas with respect to the ejector 70 in the fuel gas flow path 10.

Here, the flow rate sensor 151 for detecting the mass flow rate of the unused fuel discharged from the fuel cell module 90, and the mass of the unused fuel flowing in the recycle fuel flow path 30 among the unused fuel discharged from the fuel cell module 90. A flow rate sensor 152 for detecting the flow rate, and the electronic control unit 150 controls the pump 120 so that the circulation rate R _pv approaches the target circulation rate R _SET from the water path 50 to the merging portion of the fuel gas flow path 10. It is characterized by adjusting the amount of water supplied to the 21 side.

  Therefore, when the flow rate of the fuel gas flow path is controlled by the blower 60 to control the power generation amount of the fuel cell module 90, a high circulation rate is maintained even during startup and partial load operation (low load operation). be able to. Therefore, it is possible to provide a fuel cell system that can be operated with high efficiency over the entire load range of the fuel cell module 90.

  In the present embodiment, the unused fuel from which the water vapor has been recovered is supplied to the suction port side of the ejector 70, and the condensed water obtained by condensing the water vapor contained in the unused fuel is supplied to the junction 22 in the fuel gas flow path 10. . For this reason, while reducing the mass flow rate of the unused fuel supplied to the suction port 72 of the ejector 70 (ie, the circulating flow mass flow rate), the fuel gas flow flowing into the inlet 71a of the ejector 70 (ie, the main flow mass flow rate). The mass flow rate of can be increased. Therefore, the mass flow rate ratio (= (circulation flow mass flow / main flow mass flow) × 100%) can be lowered. For example, the conventional mass flow rate ratio of 6% to 8% becomes 0.8% to 1.2% in the present embodiment. Along with this, the suction performance of unused fuel (recycled fuel) supplied to the suction port of the ejector 70 can be afforded, and is particularly high even at low loads (ie, when the blower 60 has a small amount of blown fuel gas). A circulation rate can be obtained. Accordingly, an increase in power of the blower 60 can be suppressed to a minimum. Since the power of the pumps 110 and 120 is small in the first place, the auxiliary machine efficiency can be improved.

  In the present embodiment, when the remaining amount of condensed water in the condensed water tank 101 is equal to or less than a certain amount in step S210, the inverter circuit 160 is controlled to convert the DC voltage generated in the fuel cell module 90 into an AC voltage. And output to the electric load 170. As a result, power generation using the reformed gas is promoted in the fuel cell module 90, and water generation can be increased at the anodes of the plurality of fuel cell elements. For this reason, the quantity of the water vapor | steam contained in the unused fuel discharged | emitted from the fuel cell module 90 to the discharge flow path 20 can be increased. For this reason, the amount of water vapor contained in the unused fuel flowing through the recycled fuel flow path 30 can be increased. Along with this, the amount of condensed water condensed in the condenser 100 and stored in the condensed water tank 101 can be increased.

In this embodiment, when it is determined that the circulation rate R _PV is larger than the target circulation rate R _SET , even if the current water supply amount W _{PV is} reduced by a predetermined amount SV, the reformer 80 and the plurality of reformers 80 When it is determined that no carbon deposition occurs in the fuel cell element, the amount of water supplied per unit time flowing from the water path 50 to the merging portion 22 of the fuel gas channel 10 is reduced by a predetermined amount SV. This makes it possible to control the amount of water supplied from the water path 50 to the joining portion 22 of the fuel gas flow path 10 so as to avoid carbon deposition in the reformer 80 and the plurality of fuel cell elements. For this reason, deterioration of the reformer 80 and the plurality of fuel cell elements can be avoided.

(Other embodiments)
In the above embodiment, the installation type fuel cell system 1 has been described as the fuel cell system of the present invention, but the fuel cell system of the present invention may be replaced with the vehicle-mounted fuel cell system 1 instead.

  In the above-described embodiment, an example in which the unused fuel is cooled by the oxidizing agent in the condenser 100 to condense the water vapor has been described, but instead, the water vapor contained in the unused fuel in the condenser 100 is converted to water (for example, tap water). Water) may be cooled to condense the water vapor contained in the unused fuel. In this case, the water is heated by the unused fuel in the condenser 100 to generate hot water.

  In the above-described embodiment, the example in which the ejector 70 is disposed between the blower 60 and the reformer 80 in the fuel gas channel 10 has been described, but instead, the reformer 80 and the fuel gas channel 10 in the fuel gas channel 10 are described. The ejector 70 may be disposed between the fuel cell modules 90.

  In the above embodiment, the example in which the condenser 100 is provided in the recycle fuel flow path 30 has been described, but instead, the condenser 100 may be provided in the discharge flow path 20. For example, the condenser 100 may be provided between the fuel cell module 90 and the diverter 21 in the discharge channel 20.

  In the above embodiment, an example in which a solid oxide fuel cell is used as a fuel cell element has been described. However, instead of this, a fuel cell other than a solid oxide fuel cell may be used as a fuel cell element. .

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel gas flow path 20 Discharge flow path 30 Recycle fuel flow path 40 Oxidant flow path 50 Water flow path 60 Blower 70 Ejector 80 Reformer 90 Fuel cell module 100 Condenser 110 Pump 120 Pump 140 Combustion chamber 150 Electron Control device 151 Flow rate sensor 152 Flow rate sensor 153 Residual water amount sensor

Claims (11)

A reformer (80) for generating reformed gas from fuel gas;
A fuel cell module (90) comprising at least one fuel cell element that generates electrical energy by an electrochemical reaction between a reformed gas generated by the reformer and an oxidant;
A fuel gas flow path (10) for supplying the fuel gas to the fuel cell module side;
A condenser (100) that condenses water vapor that is not used in the electrochemical reaction and that is contained in unused fuel discharged from the fuel cell module to recover condensed water;
A recycled fuel channel (30) for returning the unused fuel from which the water vapor has been recovered by the condenser to the fuel gas channel side;
A nozzle part (71) provided in the fuel gas flow path and injecting the fuel gas, and a suction port for sucking the unused fuel from the recycled fuel flow path side by a fuel gas flow injected from the nozzle part ( 72), and an ejector (70) for mixing the fuel gas injected from the nozzle part and the unused fuel sucked from the suction port and discharging the mixed fuel to the inlet side of the fuel cell module;
A water path (50) for supplying condensed water recovered by the condenser to the upstream side of the fuel gas flow with respect to the nozzle portion of the fuel gas flow path;
A pump (120) for adjusting the amount of water supplied from the water path to the fuel gas flow path;
First detection means (151) for detecting a mass flow rate of unused fuel discharged from the fuel cell module;
Second detection means (152) for detecting a mass flow rate of unused fuel passing through the recycled fuel flow path;
The pump is controlled to supply the circulation rate, which is the ratio of the detection value of the second detection means to the detection value of the first detection means, from the water path to the fuel gas flow path side so as to approach the target value. And a control means (S120 to S160) for adjusting the amount of water to be produced. The control means controls the regulator so that a steam carbon ratio, which is a molar flow rate ratio of carbon based on water vapor and fuel gas supplied to the reformer, is equal to or higher than a preset value. The amount of water supplied to the fuel gas flow path is adjusted,
2. The fuel cell system according to claim 1, wherein the preset value is a value set so as to avoid carbon deposition in the reformer and the fuel cell element. 3. A discharge passage (20) for flowing unused fuel discharged from the discharge port of the fuel cell module to the discharge port (41) side;
The recycle fuel flow path is connected to the discharge flow path so that a part of unused fuel flowing in the discharge flow path flows to the fuel gas flow path side. Fuel cell system.   The fuel cell system according to claim 3, wherein the condenser is disposed in the recycled fuel flow path.   4. The fuel according to claim 3, wherein the condenser is connected between the fuel cell module and a branch point (21) to which the recycled fuel channel is connected in the discharge channel. Battery system. A blower (60) for generating a flow of the fuel gas flowing toward the inlet side of the nozzle portion of the ejector;
A rated power generation control means (150) for controlling the mass flow rate of the fuel gas supplied to the inlet side of the nozzle portion of the ejector by the blower so as to perform the rated power generation in the fuel cell module;
When the rated power generation control unit controls the blower so that rated power generation is performed by the fuel cell module, the amount of water vapor contained in the recycled fuel flowing in the recycled fuel flow path is the reforming of the catalyst of the reformer. The fuel cell system according to any one of claims 1 to 5, wherein the circulation rate is set so as to exceed an amount of water vapor necessary for the reaction.   The fuel cell system according to claim 6, wherein the circulation rate is set to 60% or more. The condenser includes a raw water tank (101) for temporarily storing the condensed water and supplying the stored condensed water to the fuel supply path.
A residual water amount detecting means (S153) for detecting the amount of water in the raw water tank;
Determination means (S210) for determining whether or not the amount of water detected by the residual water amount detection means is less than or equal to a set amount;
Supply means (160) for supplying electric energy generated in the fuel cell element to an electric load;
Control means for controlling the supply means so that the electric energy generated in the fuel cell element is supplied to a load when the determination means determines that the amount of water detected by the residual water amount detection means is equal to or less than a set amount. The fuel cell system according to any one of claims 1 to 7, further comprising S220).   The fuel cell system according to any one of claims 1 to 8, wherein the condenser cools and condenses water vapor contained in the unused fuel by the oxidant.   The fuel cell system according to any one of claims 1 to 8, wherein the condenser cools and condenses water vapor contained in the unused fuel with water.   11. The fuel according to claim 1, wherein the ejector is disposed on the upstream side of the flow of the fuel gas with respect to the reformer in the fuel gas flow path. Battery system.

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