JP5358357B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As a conventional fuel cell system, a reformer that generates reformed gas containing hydrogen by reforming raw fuel such as kerosene and liquefied petroleum gas, hydrogen in the reformed gas, and oxygen in the air And a fuel cell that generates electricity by causing them to undergo an electrochemical reaction (see, for example, Patent Document 1). In this fuel cell system, a diaphragm pump capable of delivering a fluid such as gas or liquid by reciprocating the diaphragm is used.

JP 2002-293504 A

  In recent years, the fuel cell system as described above has been spreading to general households, and therefore further improvement in reliability is desired. In the conventional fuel cell system, when the outside air is at a low temperature, the flow rate that can be delivered may decrease due to the temperature of the diaphragm of the diaphragm pump. At this time, the flow rate can be fed back to the control value of the diaphragm pump, but it takes a certain time to obtain a desired flow rate, which may affect the reliability of the fuel cell system.

  Therefore, an object of the present invention is to provide a fuel cell system capable of improving reliability.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a diaphragm pump that sends out a fluid according to an input control value, and a diaphragm so that the flow rate of the fluid that is sent out by the diaphragm pump becomes a predetermined flow rate. Control value output means for inputting a control value to the pump, and the control value output means changes the control value when starting the diaphragm pump based on the temperature.

  In the fuel cell system according to the present invention, the control value output means can change the control value when starting the diaphragm pump based on the temperature. Therefore, since the diaphragm pump can be started in consideration of the influence of the diaphragm on the temperature, it is possible to obtain a desired flow rate from the starting stage as compared with the control in which the flow rate is simply fed back to the control value. Thereby, the reliability of the fuel cell system can be improved.

  In the fuel cell system according to the present invention, it is preferable that the control value output means increases the control value at the time of starting the diaphragm pump as the temperature is lower. As a result, even if the flow rate is lowered due to the temperature being lowered and the diaphragm is affected, by increasing the control value at the time of starting the diaphragm pump, the flow rate is not lowered and the flow rate is reduced. A desired flow rate can be obtained. Thereby, the reliability of the fuel cell system can be further improved.

  In the fuel cell system according to the present invention, it is preferable that the diaphragm pump delivers raw fuel. About the diaphragm pump for sending the raw fuel, it is possible to send the raw fuel at a desired flow rate to the reformer from the starting stage regardless of the temperature.

  In the fuel cell system according to the present invention, the diaphragm pump preferably sends out air. About the diaphragm pump for air sending, air of a desired flow rate can be sent to the reformer and the CO remover from the start-up stage regardless of the temperature.

  According to the present invention, it is possible to improve the reliability of the fuel cell system.

1 is a schematic configuration diagram of an embodiment of a fuel cell system according to the present invention. It is the structure schematic in the characteristic part of the fuel cell system of this embodiment. It is sectional drawing which shows the structure of a fuel pump and an air pump. It is a flowchart which shows operation | movement of the fuel cell system concerning this embodiment. It is a chart which shows the example of an addition value. It is the diagram which showed the relationship between the control value of a diaphragm pump, and the flow volume of a fluid.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic configuration diagram of an embodiment of a fuel cell system according to the present invention. As shown in FIG. 1, a fuel cell system 1 includes a reformer 2 that generates reformed gas by reforming raw fuel, and a polymer electrolyte fuel cell that generates power using the reformed gas. 3 is provided. The fuel cell system 1 is used as a household power supply source, and liquefied petroleum gas (LPG) is used as a raw fuel.

  A desulfurizer 4 is disposed between the raw fuel supply source and the reformer 2. The desulfurizer 4 desulfurizes the raw fuel introduced from the outside with a desulfurization catalyst. On the upstream side of the desulfurizer 4, an electromagnetic valve 21, a tank 22, and an electromagnetic valve 23 that control the supply of raw fuel to the fuel cell system 1 are sequentially provided. On the other hand, an electromagnetic valve 24 is provided on the downstream side of the desulfurizer 4. When the fuel cell system 1 is stopped, the electromagnetic valves 23 and 24 are closed, but the internal pressure of the desulfurizer 4 is reduced by the desulfurization catalyst. For this reason, when the fuel cell system 1 is activated, the sudden opening of the raw fuel into the fuel cell system 1 is prevented by controlling the opening and closing of the electromagnetic valves 21 and 23. A fuel pump 25 is provided on the downstream side of the desulfurizer 4 and the electromagnetic valve 24. The fuel pump 25 supplies raw fuel to the reformer 2.

  The reformer 2 reforms the raw fuel with the reforming catalyst to generate a reformed gas containing hydrogen. The reformer 2 has a vaporizer (not shown) that vaporizes water supplied by the water pump 27, and generates reformed gas using steam and gaseous raw fuel.

  Since the steam reforming reaction is an endothermic reaction, the reformer 2 is provided with a burner 10 for heating the reforming catalyst. The burner 10 is connected to a supply path for raw fuel introduced by the fuel pump 25 described above. The downstream side of the fuel pump 25 described above is branched into a fuel supply path to the reformer 2 and a fuel supply path to the burner 10, and the fuel supply path is selected by opening / closing operation of the electromagnetic valve 26. Controlled. In addition, air that has been pumped by the air pump 28 is introduced into the burner 10. The exhaust gas generated by the combustion of the burner 10 is recovered through the heat exchanger 31 and exhausted to the outside.

  The reformed gas generated by the reformer 2 is introduced into a CO remover 6 disposed on the downstream side of the reformer 2. The CO remover 6 selectively oxidizes carbon monoxide contained in the reformed gas and converts it into carbon dioxide in order to reduce the carbon monoxide concentration in the reformed gas. The CO remover 6 selectively oxidizes using the air fed by the air pump 29.

  The reformed gas processed by the CO remover 6 is introduced into a humidifier 7 disposed on the upstream side of the fuel cell 3. The humidifier 7 stores water therein, and humidifies the reformed gas by allowing the introduced reformed gas to pass through as bubbles. The humidified reformed gas is supplied to the anode of the fuel cell 3.

  Further, the air pumped by the air pump 8 is introduced into the humidifier 9 disposed on the upstream side of the fuel cell 3. The humidifier 9 stores water therein and humidifies the air by passing the introduced air as bubbles. The humidified air is supplied to the cathode of the fuel cell 3.

  The fuel cell 3 is configured as a stack structure in which a plurality of battery cells are stacked. Each battery cell has an anode, a cathode, and a polymer membrane disposed therebetween. As described above, the reformed gas and air supplied to the fuel cell 3 are humidified because the polymer membrane is humidified in order to maintain high conductivity of the polymer membrane that is the electrolyte of the fuel cell 3. It is necessary to do this. In each battery cell of the fuel cell 3, hydrogen in the reformed gas supplied to the anode and oxygen in the air supplied to the cathode cause an electrochemical reaction to generate DC power.

  The electric power generated in the fuel cell 3 is supplied to the home via a converter and an inverter (not shown). The converter transforms the voltage of DC power. The inverter converts the transformed power from direct current to alternating current.

  By the way, the excess of the water vaporized into the reformed gas and supplied to the anode of the fuel cell 3 circulates and is stored again in the humidifier 7. On the other hand, the surplus (cathode drain) of the water vaporized in the air and supplied to the cathode of the fuel cell 3 is stored in the water recovery tank 13. The water stored in the humidifier 9 is supplied to the fuel cell 3 by the water pump 34 as cooling water. The cooling water is heated by the heat generated by the fuel cell 3 and returned to the humidifier 9.

  The water stored in the humidifiers 7 and 9 is introduced into the water treatment system 30 including the water recovery tank 13, the water pump 41, and the ion exchanger 14 every predetermined time. The water introduced from the humidifiers 7 and 9 into the water treatment system 30 is circulated and supplied to the ion exchanger 14 by the water pump 41 and then returned to the humidifiers 7 and 9. The water pump 27 that supplies water to the reformer 2 is connected to the water treatment system 30, and the drain contained in the exhaust gas of the burner 10 is accommodated in the water recovery tank 13.

  In addition, the surplus (so-called off-gas) of the reformed gas supplied to the anode of the fuel cell 3 is recovered through the heat exchanger 33, and then the reformer 2 is used to heat the reforming catalyst. It is used as fuel for the burner 10 provided in When the fuel cell system 1 is started, the raw fuel desulfurized by the desulfurizer 4 by switching the electromagnetic valve 26 is used as the fuel for the burner 10. On the other hand, the surplus of the air supplied to the cathode of the fuel cell 3 is recovered through the heat exchanger 32 and exhausted to the outside.

  Further, the fuel cell system 1 is connected to a hot water storage unit A in which household water is stored. The water stored in the hot water storage unit A is introduced into the heat recovery system from the inlet 15, circulated through the heat recovery system by the water pump 35, and then returned to the hot water storage unit A from the outlet 16. This heat recovery system is provided with heat exchangers 32 and 33 for recovering exhaust heat of the fuel cell 3, a heat exchanger 31 for recovering heat from the exhaust gas of the burner 10, and a cooling circuit for cooling the fuel cell 3 body. A heat exchanger (not shown) and the like are included. Hot water is transferred through the heat recovery system.

  The operation of the components of the fuel cell system 1 described above is controlled by electrical devices (not shown). The electrical equipment controls the constituent equipment according to the sensors provided in the fuel cell system 1 and the usage status of the user. Examples of the sensors include a thermometer 36 that detects the ambient temperature, a pressure gauge 37 that is disposed between the solenoid valves 21 and 23, a flow meter 38 that is provided downstream of the fuel pump 25, and a downstream of the air pump 29. A flow meter 39 provided on the side, a flow meter 51 provided on the downstream side of the air pump 28, and the like are used.

  The outline of the basic operation of the fuel cell system 1 will be described. The fuel cell system 1 performs a negative pressure elimination process of the desulfurizer 4 after the system is started. Thereafter, raw fuel and air are supplied to the burner 10 by the fuel pump 25 and the air pump 28. In addition, water is circulated by the water pump 41 in the water treatment system 30, and the cooling water of the fuel cell 3 is circulated by the water pump 34.

  On the other hand, when the temperature of the reformer 2 is stabilized by the combustion of the burner 10, the supply path of the raw fuel is changed by the electromagnetic valve 26 and the raw fuel is supplied to the reformer 2. Further, water of the water treatment system 30 is supplied to the reformer 2 by the water pump 27. The reformer 2 generates a reformed gas using raw fuel and water, and supplies the generated reformed gas to the CO remover 6. In addition, air is supplied to the CO remover 6 by the air pump 29. Then, the reformed gas from which CO has been removed by the CO remover 6 is supplied to the humidifier 7, humidified and supplied to the anode. Then, the anode off gas is supplied to the burner 10. In addition, air is supplied to the humidifier 9 by the air pump 8, humidified and supplied to the cathode. As a result, power is generated in the fuel cell 3 and electric power is supplied to the home. The electrical equipment controls the amount of raw fuel and water supplied to the reformer 2, the amount of air supplied to the CO remover 6, the pump output, etc., based on the power used by the user and the output of the sensors. To perform stable operation and optimum operation.

  Next, the structure in the characteristic part of embodiment of this invention is demonstrated in detail with reference to FIG.2 and FIG.3. FIG. 2 is a schematic configuration diagram of a characteristic portion of the fuel cell system according to the present embodiment. FIG. 3 is a cross-sectional view showing configurations of the fuel pump 25 and the air pump 28. FIG. 2 shows a control unit (control value output means) 100 that controls the entire fuel cell system 1, a reformer 2, a fuel pump 25, an air pump 28, a thermometer 36, a flow meter 38, and a flow meter 51. The connection relationship is indicated by a one-dot chain line. Although not shown in FIG. 2, other devices of the fuel cell system 1 are also connected to the control unit 100.

  As shown in FIG. 2, the control unit 100 is electrically connected to the reformer 2 and has a function of outputting a signal for operating the igniter of the burner 10 of the reformer 2. The control unit 100 is electrically connected to the fuel pump 25 and the air pump 28, and sets a control value corresponding to the target flow rate (predetermined flow rate) of the fuel and outputs the control value to the fuel pump 25. 25, and a function of driving the air pump by setting a control value corresponding to the target flow rate of air and outputting it to the air pump 28. The control unit 100 is electrically connected to the thermometer 36, the flow meter 38 and the flow meter 51, the ambient temperature of the fuel cell system 1 detected by the thermometer 36, and the fuel sent from the fuel pump 25. And the flow rate of air sent from the air pump 28 are obtained from each sensor.

  As shown in FIG. 3, the fuel pump 25 and the air pump 28 are diaphragm pumps. The diaphragm pump includes a moving body 61 arranged so as to be able to reciprocate, an electromagnet 62 arranged so as to surround the moving body 61, and diaphragms 63, 64 whose central portions are made reciprocally movable by the movement of the moving body 61. , A suction port 65 through which fluid is sucked and a discharge port 66 through which fluid is discharged. In the diaphragm pump, the moving body 61 reciprocates when an alternating current flows through the electromagnet 62, and the diaphragms 63, 64 reciprocate accordingly, thereby sucking fluid from the suction port 65 and from the discharge port 66. Fluid is pumped. Specifically, when the moving body 61 performs a forward movement (the direction indicated by A in the figure), the diaphragm 63 moves forward to increase the volume of the internal space 67 and from the suction port 65 through the valve. Fluid flows in. Further, when the diaphragm 64 moves forward, the volume of the internal space 68 decreases, and the fluid is pumped from the discharge port 66 through the valve. On the other hand, when the moving body 61 performs the backward movement, the diaphragm 63 and the diaphragm 64 are moved backward, so that the volume of the internal space 67 is decreased and the volume of the internal space 68 is increased. The fluid is supplied from the internal space 67 to the internal space 68 via the. The delivery flow rate of the diaphragm pump can be controlled by a control value input to the electromagnet 62. In the diaphragm pump, when the temperature is low, the diaphragms 63 and 64 are affected by the temperature, so that the delivery flow rate is lowered.

Returning to FIG. 2, in the present embodiment, the control unit 100 acquires the flow rate of the fuel sent by the fuel pump 25 from the flow meter 38, feeds back the flow rate, sets a control value, and controls the fuel pump 25. A value can be output. In addition, the control unit 100 can acquire the flow rate of air sent from the air pump 28 from the flow meter 51, feed back the flow rate, set a control value, and output the control value to the air pump 28. That is, when the flow rate detected by the flow meter is larger than the target flow rate, the control unit 100 decreases the delivery flow rate by setting the control value to be smaller, and when the flow rate detected by the flow meter is smaller than the target flow rate. The feed flow rate can be increased by setting a large control value.

  Further, the control unit 100 has a function of changing control values when the fuel pump 25 and the air pump 28 are started based on the temperature detected by the thermometer 36. That is, the control unit 100 can increase the control value at the time of starting the fuel pump 25 and the air pump 28 as the temperature detected by the thermometer 36 is lower. Specifically, the control unit 100 sets an initial input value that is predetermined for the target flow rate as a set value at room temperature (for example, when the temperature is higher than a predetermined temperature threshold). On the other hand, the control unit 100 sets a value obtained by adding an added value to the initial input value as a control value at a low temperature (for example, when the temperature is equal to or lower than a predetermined temperature threshold). The threshold value for determining normal temperature and low temperature is not particularly limited. The added value is set according to the temperature, and the lower the temperature, the greater the influence on the diaphragm. Therefore, it is preferable to set a larger value as the temperature is lower. The installation location of the thermometer 36 is not particularly limited as long as the ambient temperature of the fuel cell system 1 can be acquired. The thermometer 36 may be installed in a housing in which each component of the fuel cell system 1 is accommodated. You may install in. Also when installing in a housing, the position in a housing is not specifically limited.

  Next, the operation of the fuel cell system 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the fuel cell system 1 according to this embodiment. The process of FIG. 4 is executed in the control unit 100 and executed when the burner 10 of the reformer 2 is ignited when the fuel cell system 1 is started.

  As shown in FIG. 4, the control unit 100 activates the air pump 28 with the activation of the fuel cell system 1 (step S <b> 10). Next, the control unit 100 determines whether the ambient temperature is low or normal based on the ambient temperature detected by the thermometer 36 (step S12). In the process of S12, specifically, it is determined whether the ambient temperature detected by the thermometer 36 is equal to or lower than a preset temperature threshold (in this embodiment, for example, 5 ° C.). When it is determined in S12 that the ambient temperature is higher than the temperature threshold, the control unit 100 determines that the ambient temperature is normal temperature, sets the initial input value corresponding to the target flow rate to the control value, and activates the air pump 28. (Step S14).

  On the other hand, if it is determined in step S12 that the ambient temperature is equal to or lower than the temperature threshold, the control unit 100 determines that the ambient temperature is low, and adds the added value to the initial input value corresponding to the target flow rate. Is set to a control value, and the air pump 28 is started (step S16). The added value to be added increases as the temperature decreases. For example, as shown in FIG. 5, when the ambient temperature is 5 ° C., the added value = 25, when the ambient temperature is 0 ° C., the added value = 50, and when the ambient temperature is −5 ° C., the added value = 75. When the ambient temperature is −10 ° C., the added value = 100.

  After starting the air pump 28 in S14 or S16, the control unit 100 performs feedback based on the flow rate detected by the flow meter 51 (step S18). Specifically, the control unit 100 compares the flow rate detected by the flow meter 51 with the target flow rate, and if the detected flow rate is lower than the target flow rate, the control value output to the air pump 28 is increased, and the detected flow rate is When the target flow rate is exceeded, the control value output to the air pump 28 is decreased. Then, the control part 100 operates the igniter of the burner 10 of the reformer 2 (step S20).

  After the process of S20, the control unit 100 activates the fuel pump 25 (step S22). Next, the control unit 100 determines whether the ambient temperature is a low temperature or a normal temperature based on the ambient temperature detected by the thermometer 36 (step S24). In the process of S24, specifically, it is determined whether the ambient temperature detected by the thermometer 36 is equal to or lower than a preset temperature threshold value (in this embodiment, for example, 5 ° C.). When it is determined in S24 that the ambient temperature is higher than the temperature threshold, the control unit 100 determines that the ambient temperature is normal temperature, sets the initial input value corresponding to the target flow rate to the control value, and sets the fuel pump 25. Start (step S26).

  On the other hand, when it is determined in the process of S24 that the ambient temperature is equal to or lower than the temperature threshold, the control unit 100 determines that the ambient temperature is a low temperature and adds the added value to the initial input value corresponding to the target flow rate. Is set to a control value, and the fuel pump 25 is started (step S28). The added value to be added becomes larger as the temperature is lower. For example, the value shown in FIG. 5 can be used. In this embodiment, the temperature threshold value and the added value of the fuel pump 25 are the same as those of the air pump 28, but different values may be used. For example, when a diaphragm pump having different performance is applied to the fuel pump 25 and the air pump 28, or when a target flow rate is different between the fuel pump 25 and the air pump 28, a different temperature threshold value or a different added value is used. May be.

  After starting the fuel pump 25 in S26 or S28, the control unit 100 performs feedback based on the flow rate detected by the flow meter 38 (step S30). Specifically, the control unit 100 compares the flow rate detected by the flow meter 38 with the target flow rate, and when the detected flow rate is lower than the target flow rate, increases the control value output to the fuel pump 25 to detect the detected flow rate. If the value exceeds the target flow rate, the control value output to the fuel pump 25 is decreased. After the process of S30, the control unit 100 performs ignition confirmation of the burner 10, and ends the process shown in FIG.

  Next, the operation and effect of the fuel cell system 1 according to this embodiment will be described with reference to FIG. FIG. 6 is a diagram showing the relationship between the control value of the diaphragm pump applied to the fuel pump 25 or the air pump 28 and the flow rate of the fluid.

  FIG. 6A shows the relationship between the control value and the flow rate at normal temperature, the graph CV1 in the figure shows the control value output to the diaphragm pump, and the graph FR1 shows the flow rate of the fluid to be sent. Yes. FIG. 6B shows the relationship between the control value and the flow rate at the time of low temperature for the conventional fuel cell system, that is, the control value when the control value is set without adding anything to the initial input value even at low temperature. The flow rate relationship is shown. In FIG. 6B, a graph CV2 indicates the control value output to the diaphragm pump, and a graph FR2 indicates the flow rate of the fluid to be delivered. FIG. 6C shows the relationship between the control value and the flow rate when the fuel cell system 1 according to the present embodiment is at a low temperature. A graph CV3 in the drawing shows a control value output to the diaphragm pump, and a graph FR3 Indicates the flow rate of the fluid to be delivered. In FIG. 6, the horizontal axis represents time.

  As shown in FIG. 6 (a), at the normal temperature, when the initial input value A is input to the pump as a control value when the pump is started as shown in the control value graph CV1, the target is immediately set as shown in the flow rate graph FR1. The flow rate B can be obtained. However, at a low temperature, the flow rate that the diaphragm can deliver due to the influence of temperature decreases. As shown in FIG. 6 (b), in the conventional fuel cell system, when the initial input value A is input to the pump as a control value at the time of starting the pump as shown in the control value graph CV2, as shown in the flow rate graph FR2, When the pump is started, the flow rate does not reach the target flow rate B, and the target flow rate B is reached by performing feedback for a predetermined time to gradually increase the control value.

  As described above, in the conventional fuel cell system, the target flow rate can be obtained by feeding back the flow rate to the control value of the diaphragm pump at a low temperature, but it takes a certain time to obtain the desired flow rate. As a result, the reliability of the fuel cell system may be affected.

  On the other hand, as shown in FIG. 6C, in the fuel cell system 1 according to the present embodiment, as shown in the control value graph CV3, the value obtained by adding the addition value C to the initial input value A when the pump is started. Is output as a control value. As a result, as shown in the flow rate graph FR3, the target flow rate B can be obtained immediately after the pump is started.

  As described above, in the fuel cell system 1 according to the present embodiment, the control unit 100 can change the control value when the diaphragm pump is started based on the temperature. Therefore, since the diaphragm pump can be started in consideration of the influence of the diaphragm on the temperature, it is possible to obtain a desired flow rate from the starting stage as compared with the control in which the flow rate is simply fed back to the control value. Thereby, the reliability of the fuel cell system 1 can be improved.

  Further, in the fuel cell system 1 according to the present embodiment, the control unit 100 increases the control value when starting the diaphragm pump as the temperature is lower. As a result, even if the flow rate is lowered due to the temperature being lowered and the diaphragm is affected, by increasing the control value at the time of starting the diaphragm pump, the flow rate is not lowered and the flow rate is reduced. A desired flow rate can be obtained. Thereby, the reliability of the fuel cell system 1 can be further improved.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the diaphragm pump is used for the fuel pump 25 and the air pump 28, but one of the pumps other than the diaphragm pump may be used. In this case, the present invention is applied to one pump to which a diaphragm pump is applied. In the above-described embodiment, only the fuel pump 25 and the air pump 28 have been described. However, the present invention may be applied to other pumps (for example, the air pump 29) to which the diaphragm pump is applied in the fuel cell system 1. Good.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 25 ... Fuel pump (diaphragm pump), 28 ... Air pump (diaphragm pump), 100 ... Control part (control value output means).

Claims (2)

A diaphragm pump that delivers either raw fuel or air according to the input control value;
The one of the flow rate of the raw fuel or air is delivered by a diaphragm pump is a fuel cell system Ru and a control value output means for inputting said control value to said diaphragm pump to a predetermined flow rate,
The control value output means changes the control value at the start of the diaphragm pump based on the ambient temperature of the fuel cell system ,
The control value output means increases the control value at the start of the diaphragm pump as the ambient temperature is lower,
The control value output means changes the control value based on the ambient temperature when starting the fuel cell system, and after starting the fuel cell system, either the raw fuel or the air sent out by the diaphragm pump. The fuel cell system is characterized in that the control value is changed by feeding back the flow rate . The control value output means inputs the control value to which the added value based on the ambient temperature is added to the diaphragm pump if the ambient temperature is equal to or lower than a predetermined threshold when the fuel cell system is started. The fuel cell system according to claim 1.

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