JP2005135805A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of controlling temperature of a burner. <P>SOLUTION: The fuel cell system comprises a fuel cell 3, a hydrogen module 4 for resupplying nitrogen and part of unreacted hydrogen containing water exhausted from the fuel cell 3 to the fuel cell 3, a burner 7 for burning the exhausted hydrogen from the fuel cell 3, a nitrogen concentration detecting device 13 and a moisture detecting device 14 for respectively detecting nitrogen concentration and moisture amount in the exhausted hydrogen exhausted from the fuel cell 3, and a temperature sensor 12 for detecting temperature of the burner 7. The fuel cell system further comprises a bypass passage 9 for bypassing the burner 7 to control the flow of the exhausted hydrogen gas to the bypass passage according to the results from the nitrogen concentration detecting device 13, the moisture detecting device 14, and the temperature sensor 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to treatment of discharged hydrogen discharged from a fuel cell.

Conventionally, the hydrogen gas discharged from the fuel cell contains nitrogen and moisture from the air electrode side of the fuel cell in addition to hydrogen that was not used in the fuel cell, and these components contribute to the power generation efficiency of the fuel cell. Patent Document 1 discloses that when the concentration increases, the fuel is burned in a combustor and then released to the outside and the heat of combustion is used for fuel reforming.
JP 2003-77517 A

  However, in the conventional invention, since all of the exhaust hydrogen gas discharged from the fuel cell is sent to the combustor, the temperature of the combustor cannot be controlled, and deterioration of the combustor due to temperature rise or moisture in the exhaust hydrogen gas This causes the problem that the combustor misfires.

  The present invention has been invented to solve such problems, and aims to control the exhaust hydrogen gas supplied to the combustor and stabilize the temperature of the combustor.

  In the present invention, in the fuel cell system, a part of the discharged hydrogen gas discharged from the fuel cell is supplied again to the fuel cell, and the discharge means for discharging the remaining discharged hydrogen gas, and the discharged hydrogen gas is discharged from the fuel cell. Combustion means for burning the exhausted hydrogen gas, exhaust hydrogen gas state detecting means for detecting the state of the exhausted hydrogen gas, temperature detecting means for detecting the temperature of the combustion means, and a bypass circuit for bypassing the combustion means. Further, a flow rate control means is provided for controlling the flow rate of the exhaust hydrogen gas flowing through the bypass circuit according to the state of the exhaust hydrogen gas and the temperature of the combustion means.

  According to the present invention, for example, the temperature of the combustion means is controlled by the exhaust hydrogen gas bypassing the combustion means according to the nitrogen concentration and water content in the discharged hydrogen discharged from the fuel cell or the temperature of the combustion means. be able to.

  The configuration of the first embodiment of the present invention will be described with reference to the configuration diagram of FIG.

  The fuel cell system includes a hydrogen tank 1, an air supply device 2, a fuel cell 3, a hydrogen module 4, and a combustor 7. Further, a pipe 8 that connects the hydrogen module 4 and the combustor 7 and a pipe 11 that connects the fuel cell 3 and the combustor 7 are provided. The pipe 8 is provided with an on-off valve 5 in the middle thereof, and is provided with a bypass pipe 9 which is a bypass circuit for bypassing the combustor 7 from between the on-off valve 5 and the combustor 7. The bypass pipe 9 has a flow rate for adjusting the opening degree. A variable opening valve 6 which is a control means is provided.

  The air supply device 2 uses, for example, a blower, takes in air from the outside, and supplies the air to the fuel cell 3.

  The fuel cell 3 generates power using the hydrogen supplied from the hydrogen tank 1 via the hydrogen module 4 and the air supplied from the air supply device 2. In the anode (not shown) of the fuel cell 3, nitrogen and water are mixed from a cathode (not shown), and the mixed nitrogen and water are recovered to the hydrogen module 4 together with hydrogen not used in the reaction.

  The hydrogen module 4 supplies the hydrogen supplied from the hydrogen tank 1 to the fuel cell 3, and collects exhausted hydrogen containing nitrogen and moisture discharged from the anode after the reaction in the fuel cell 3. The recovered discharged hydrogen has its nitrogen concentration detected by a nitrogen concentration detecting device 13 which is a nitrogen concentration detecting means provided in the hydrogen module 4 and its water content is detected by a moisture detecting device 14 which is a water content detecting means. Depending on the nitrogen concentration and water content, a part of the recovered exhausted hydrogen is discharged to the combustor 7 via the pipe 8 and the remaining discharged hydrogen is supplied to the fuel cell 3 again. The flow rate discharged to the combustor 7 is controlled by the on-off valve 5 which is a discharge hydrogen gas flow rate control means provided in the pipe 8 according to the nitrogen concentration and water content (the hydrogen module 4 is a discharge means).

  The combustor 7 is supplied with hydrogen containing nitrogen and water discharged from the hydrogen module 4 through the pipe 8, and supplied with air discharged from the fuel cell 3 through the pipe 11. Then, the supplied air and hydrogen are combusted, and the combustion gas is discharged to the outside through the pipe 10. The combustor 7 includes a temperature sensor 12 and detects the temperature of the combustor 7 by the temperature sensor 12 which is a temperature detection means (the combustor 7 is a combustion means).

  The bypass flow path 9 branches from a pipe 8 connecting the hydrogen module 4 and the combustor 7, bypasses the combustor 7, and joins the pipe 10 downstream of the combustor 7. As a result, part of the discharged hydrogen discharged from the hydrogen module 4 bypasses the combustor 7 and is discharged to the outside. Further, the flow rate of the discharged hydrogen flowing into the combustor 7 and the bypass flow path 9 is adjusted by adjusting the variable opening valve 6 provided in the bypass flow path 9.

  A controller 30 is provided for controlling the on-off valve 5 and the regulating valve 6 based on respective signals detected from the temperature sensor 12, the nitrogen concentration detection device 13, and the moisture detection device 14.

  Next, the control operation performed by the controller 30 will be described with reference to the flowchart of FIG. As an initial state, the on-off valve 5 is closed.

  After the fuel cell system is started up, it is discharged from the anode by power generation of the fuel cell 3 and unreacted discharged hydrogen containing nitrogen and water is circulated again to the anode of the fuel cell 3 and used as fuel for power generation. In step S20, the nitrogen concentration detector 13 detects the nitrogen concentration dn in the discharged hydrogen in the hydrogen module 4, and the moisture detector 14 detects the water content w in the discharged hydrogen in the hydrogen module 4.

  In step S21, the nitrogen concentration dn detected in step S20 and the water content w are compared with threshold values d1 and w1 set in advance. If at least one of the values exceeds the threshold value, the process proceeds to step S22 to open / close The valve 5 is opened and discharged hydrogen is discharged from the hydrogen module 4. When the threshold values d1 and w1 are not exceeded, the circulation of the exhaust hydrogen is continued. Here, the threshold values d1 and w1 are values that reduce the power generation efficiency of the fuel cell 3 when the amount of nitrogen or water in the exhausted hydrogen increases and the exhausted hydrogen is circulated to the fuel cell 3 again, and are obtained beforehand through experiments or the like. . As a result, the nitrogen concentration and water content in the hydrogen supplied to the fuel cell 3 can be suppressed, the reaction can be performed efficiently in the fuel cell 3, and the amount of hydrogen supplied from the hydrogen tank 1 can be reduced. Can do.

  In step S20, the opening / closing valve 5 is read according to the nitrogen concentration dn and the water content w, respectively, and the opening degree of the opening / closing valve 5 is read from the previously stored opening degree map, respectively, and according to the nitrogen concentration dn and the water content w. The opening degree of the on-off valve 5 may always be adjusted to the larger opening degree. At this time, the on-off valve 5 may not be closed in the initial state.

  In step S23, the combustion temperature T of the combustor 7 is detected, and the opening of the variable opening valve 6 corresponding to the combustion temperature T is read from the map of FIG. Moreover, the opening degree of the variable opening valve 6 corresponding to the nitrogen concentration dn and the water content w detected in step S20 is read from the maps of FIGS. The maps in FIGS. 3 to 5 are obtained in advance through experiments and the like. The higher the combustion temperature T is, and the larger the nitrogen concentration dn and the water content w are, the larger the opening of the variable opening valve 6 is.

  In step S24, the variable opening valve 6 is opened to the largest opening degree among the three opening degrees of the variable opening valve 6 corresponding to the combustion temperature T, the nitrogen concentration dn, and the water content w read in step S23. Adjust the degree. As a result, when the combustion temperature of the combustor 7 is high, the degree of opening of the variable opening valve 6 is increased, and a large amount of discharged hydrogen flows through the bypass passage 9 that bypasses the combustor 7. The temperature can be lowered. Further, when the nitrogen concentration dn or the water content w is large, the degree of opening of the variable opening valve 6 is increased, and a large amount of discharged hydrogen flows through the bypass passage 9 that bypasses the combustor 7. Misfire of the combustor 7 due to water can be prevented.

  Here, from the temperature of the combustor 7 and the water content of the discharged hydrogen, for example, when the temperature of the combustor 7 is high and the water content is high, the temperature of the combustor 7 is increased to a predetermined value such as increasing the amount of discharged hydrogen. The amount of discharged hydrogen supplied to the combustor 7 may be controlled by the variable opening valve 6 so as to be within the temperature range.

  Such a step is performed for a certain period of time or until the nitrogen concentration dn and the water content w are smaller than a certain predetermined value. Thereby, fuel consumption in the fuel cell 3 can be suppressed, and the temperature control of the combustor 7 can be performed.

  In step S21, the opening degree of the on-off valve 5 may be adjusted by the gas flow rate in the hydrogen module 4 in addition to the nitrogen concentration and water content. Similarly, in step S24, the opening of the variable opening valve 6 may be adjusted by the discharged hydrogen flow rate.

  The effect of 1st Embodiment of this invention is demonstrated.

  When the bypass passage 9 for bypassing the combustor 7 is provided and the temperature of the combustor 7 is high, the flow rate of discharged hydrogen flowing into the bypass passage 9 is increased, and the flow rate of discharged hydrogen flowing into the combustor 7 is decreased. By doing so, it is possible to prevent the temperature of the combustor 7 from becoming higher and to exceed the allowable temperature of the combustor 7, and to prevent deterioration of the combustor 7.

  Further, even when the nitrogen concentration or water content in the exhaust hydrogen is large, the flow rate of the exhaust hydrogen flowing to the bypass passage 9 is increased, the flow rate of the exhaust hydrogen flowing into the combustor 7 is decreased, and the combustor using nitrogen or water 7 can prevent misfire.

  Next, a second embodiment of the present invention will be described using the configuration diagram of FIG. The second embodiment will be described with respect to parts different from FIG.

  In this embodiment, the heat exchanger 15 which is a heat exchange means for exchanging heat with the combustor 7 is provided. The pipe 11 is provided with a variable opening valve 19 that is an air flow rate control means for controlling the amount of air supplied to the combustor 7. In the hydrogen module 4, all the hydrogen can be supplied to the combustor 7 via the pipe 8 without supplying the hydrogen supplied from the hydrogen tank 1 to the fuel cell 3. Thereby, when it is necessary to warm up the fuel cell system at the time of starting below freezing point, the heat generated by the combustor 7 is received by the heat exchanger 15 and the fuel cell system can be warmed up.

  When the fuel cell system is started up, the temperature of the outside air is detected by the temperature sensor 20 serving as the outside air temperature detecting means, and when the temperature is around a predetermined value of water or moisture solidifying temperature, or around the freezing point. Hydrogen is supplied from the hydrogen tank 1 to the combustor 7 through the hydrogen module 4 and the pipe 8, and the flow rate is adjusted by the variable opening valve 19 from the air supply device 2 through the fuel cell 3 and the pipe 11, and then the combustor Air is supplied to 7 and the combustor 7 burns hydrogen. Then, heat exchange is performed with a refrigerant or the like flowing through the heat exchanger 15, and the fuel cell system such as the fuel cell 3 is warmed up by the heat generated in the combustor 7. At this time, the variable opening valve 6 can be fully closed or set to the minimum opening, and the combustor 7 can perform fuel efficient combustion.

  Since the control operation performed by the controller 30 at the normal time is the same as that in the first embodiment, the description thereof is omitted here.

  The effect of 2nd Embodiment of this invention is demonstrated.

  When the temperature of the fuel cell system is low, such as when starting below the freezing point, the hydrogen supplied from the hydrogen tank 1 to the combustor 7 is combusted by the air whose flow rate is controlled by the variable opening valve 19 from the air supply device 2. The heat of combustion can be recovered by the heat exchanger 15, and at that time, the opening degree of the variable opening degree valve 6 is fully closed or the flow rate flowing through the bypass passage 9 is controlled to be the minimum flow rate. The combustor 7 can burn efficiently.

  Next, a third embodiment of the present invention will be described using the configuration diagram of FIG. The third embodiment will be described with respect to the differences from FIG.

  In this embodiment, the piping 8 between the piping 8 and the branch portion of the bypass flow path 9 and the combustor 7 is provided with a flow control device 18 that is a second flow control means. In addition, a check valve 16 is provided in the bypass flow path 9. Furthermore, a variable opening valve 19 that controls the amount of air supplied to the combustor 7 is provided in the pipe 11. With these configurations, the flow control device 18 adjusts the amount of discharged hydrogen supplied to the combustor 7. For example, when the flow rate is reduced by the flow control device 18 using a movable orifice, the pressure in the pipe 8 is reduced. When the pressure rises and the pressure exceeds a predetermined set value, the check valve 16 opens and a part of the discharged hydrogen can flow into the bypass passage 9.

  Next, the control operation performed by the controller 30 will be described using the flowchart of FIG. As an initial state, the on-off valve 5 is closed.

  Since steps S80 to S82 are the same control as steps S20 to S22 of the first embodiment, description thereof is omitted here.

  In step S83, the combustion temperature T of the combustor 7 is detected, and the opening degree of the flow control device 18 corresponding to the combustion temperature T is read from the map of FIG. Moreover, the opening degree of the flow control device 18 corresponding to the nitrogen concentration dn and the water content w detected in step S80 is read from the maps of FIGS. 10 and 11, respectively. The maps in FIGS. 8 to 11 are obtained in advance by experiments and the like. The higher the combustion temperature T is, and the larger the nitrogen concentration dn and the water content w are, the smaller the opening degree of the flow control device 18 is.

  In step S84, the opening degree of the flow control device 18 is set to the smallest opening degree among the opening amounts of the three flow control devices 18 corresponding to the combustion temperature T, the nitrogen concentration dn, and the water content w read out in step S83. The flow rate of the exhaust air exhausted from the cathode of the fuel cell 3 is adjusted by the variable opening valve 19. Here, when the opening degree of the flow rate control device 18 is reduced, the pressure in the pipe 8 increases, and when a certain predetermined pressure is reached, the check valve 16 is opened and the discharged hydrogen is discharged to the outside through the bypass passage 9. . This predetermined pressure is set in advance through experiments or the like, and is a pressure that prevents deterioration of the flow rate control device 18 due to an increase in pressure and can supply exhaust hydrogen to the combustor 7 accurately. When the combustion temperature of the combustor 7 is high, the degree of opening of the flow rate control device 18 is reduced, and a large amount of discharged hydrogen flows through the bypass passage 9 that bypasses the combustor 7. Can do. In addition, when the nitrogen concentration dn or the water content w is large, the opening degree of the flow rate control device 18 is reduced, and a large amount of discharged hydrogen flows through the bypass passage 9 that bypasses the combustor 7. The misfire of the combustor 7 due to can be prevented. Moreover, since the air flow rate to the combustor 7 is controlled by the variable opening valve 19, the temperature of the combustor 7 can be controlled more accurately.

  Here, from the temperature of the combustor 7 and the water content of exhaust hydrogen, for example, when the temperature of the combustor 7 is high and the water content is high, the amount of exhaust hydrogen supplied to the combustor 7 is increased. The amount of discharged hydrogen supplied to the combustor 7 may be controlled by the flow control device 18 so that the temperature falls within a certain predetermined temperature range.

  Such a step is performed for a certain period of time or until the nitrogen concentration dn and the water content w are smaller than a certain predetermined value. Thereby, fuel consumption in the fuel cell 3 can be suppressed, and the temperature control of the combustor 7 can be performed.

  In step S81, as in step S21, the opening of the on-off valve 5 may be adjusted by the gas flow rate in the hydrogen module 4 in addition to the nitrogen concentration and water content. Similarly, in step S84, the opening degree of the flow control device 18 may be adjusted by the discharged hydrogen flow rate.

  The effect of the third embodiment of the present invention will be described.

  When the flow rate control device 18 is provided in the pipe 8 connecting the hydrogen module 4 and the combustor 7 and the flow rate is reduced by the flow rate control device 18, the check valve 16 provided in the bypass flow path 9 is provided when a predetermined pressure is reached. It opens, and a part of the discharged hydrogen flows to the bypass channel 9 and is discharged to the outside, so that the discharged hydrogen can be accurately supplied to the combustor 7 and the temperature of the combustor 7 can be accurately controlled. . Moreover, since the amount of exhaust air supplied from the fuel cell 3 to the combustor 7 is adjusted by the variable opening valve 19, the temperature of the combustor 7 can be controlled more accurately.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea.

  INDUSTRIAL APPLICABILITY The present invention can be used in the field where exhausted hydrogen gas discharged from a fuel cell is burned and discharged to the outside.

It is a block diagram which shows 1st Embodiment of this invention. It is a flowchart of the control operation which the controller of 1st Embodiment of this invention performs. It is a figure which shows the opening degree of the variable opening valve with respect to the nitrogen concentration in the exhaust hydrogen in 1st Embodiment of this invention. It is a figure which shows the opening degree of the variable opening degree valve with respect to the water content in exhaust hydrogen in 1st Embodiment of this invention. It is a figure which shows the opening degree of the variable opening degree valve with respect to the combustor temperature in the exhaust hydrogen in 1st Embodiment of this invention. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram which shows 3rd Embodiment of this invention. It is a flowchart of the control operation which the controller of 3rd Embodiment of this invention performs. It is a figure which shows the opening degree of the flow control apparatus with respect to the nitrogen concentration in exhaust hydrogen in 3rd Embodiment of this invention. It is a figure which shows the opening degree of the flow control apparatus with respect to the water content in exhaust hydrogen in 3rd Embodiment of this invention. It is a figure which shows the opening degree of the flow control apparatus with respect to the combustor temperature in the exhaust hydrogen in 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogen tank 2 Air supply device 3 Fuel cell 4 Hydrogen module (discharge means)
5 On-off valve (exhaust hydrogen gas flow rate control means)
6 Variable opening valve (flow control means)
7 Combustor (combustion means)
9 Bypass passage (bypass circuit)
12 Temperature sensor (temperature detection means)
13 Nitrogen concentration detector (nitrogen concentration detector)
14 Moisture detection device (moisture content detection means)
15 Heat exchanger (heat exchange means)
18 Flow control device (flow control means)
20 Temperature sensor (outside air temperature detection means)
30 controller

Claims (9)

In a fuel cell system including a fuel cell that generates electricity by hydrogen supplied to a hydrogen electrode and an oxidant supplied to an oxygen electrode,
A discharge means for recirculating at least part of the discharged hydrogen gas discharged from the hydrogen electrode to the fuel cell again and discharging the remaining discharged hydrogen gas;
Exhaust hydrogen gas state detection means for detecting the state of the exhaust hydrogen gas circulating in the fuel cell;
Combustion means for burning the discharged hydrogen gas discharged by the discharge means;
A bypass circuit in which the exhaust hydrogen gas discharged by the discharge means bypasses the combustion means;
Temperature detecting means for detecting the temperature of the combustion means;
Depending on the state of the exhaust hydrogen gas detected by the exhaust hydrogen gas state detection means and the temperature of the combustion means detected by the temperature detection means, the flow rate of the exhaust hydrogen gas flowing to the combustion means and the bypass circuit And a flow rate control means for controlling the flow rate of the exhaust hydrogen gas flowing.   2. The fuel cell system according to claim 1, wherein the flow rate control unit increases the flow rate of the exhaust hydrogen gas flowing into the bypass circuit as the temperature of the combustion unit increases. A discharge hydrogen gas flow rate control means for controlling the flow rate of discharged hydrogen gas discharged by the discharge means;
3. The flow rate control means increases the flow rate of the exhaust hydrogen gas flowing to the bypass circuit as the flow rate of the exhaust hydrogen gas controlled by the exhaust hydrogen gas flow rate control means increases. The fuel cell system described in 1. The exhaust hydrogen gas state detection means comprises nitrogen concentration detection means for detecting the nitrogen concentration of the exhaust hydrogen gas discharged from the fuel cell,
4. The flow rate control means increases the flow rate of the exhaust hydrogen gas flowing to the bypass circuit as the nitrogen concentration detected by the nitrogen concentration detection means is higher. The fuel cell system described in 1.   5. The fuel cell system according to claim 4, wherein the exhaust hydrogen gas flow rate control means increases the exhaust hydrogen gas flow rate to be discharged as the nitrogen concentration detected by the nitrogen concentration detection means increases. The exhaust hydrogen gas state detection means comprises water content detection means for detecting the water content of the exhaust hydrogen gas discharged from the fuel cell;
The flow rate control means increases the flow rate of the exhaust hydrogen gas flowing to the bypass circuit as the amount of water contained in the exhaust hydrogen gas detected by the water content detection means increases. 6. The fuel cell system according to any one of 5 above.   The exhaust hydrogen gas flow rate control means increases the exhaust hydrogen gas flow rate to be discharged as the amount of water contained in the exhaust hydrogen gas detected by the water content detection means is higher. Fuel cell system. Heat exchange means for performing heat exchange with the combustion means and heating the fuel cell;
An outside air temperature detecting means for detecting the outside air temperature,
The flow rate of the exhaust hydrogen gas flowing through the bypass circuit is set to a minimum flow rate when the temperature detected by the temperature detection unit is lower than a predetermined value. Fuel cell system. Air flow control means for controlling the amount of air supplied to the combustion means;
The fuel cell system according to any one of claims 1 to 8, wherein an air flow rate by the air flow rate control unit is controlled in accordance with a flow rate of the exhaust hydrogen gas supplied to the combustion unit.

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