JP2005071748A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel reforming system with improved responsiveness when a required load fluctuates.
In a fuel cell system comprising a fuel cell stack (12) and a reforming system for supplying hydrogen-rich reformed gas to the fuel cell stack, heat generated in the reforming system is recovered and reformed. The first evaporator 6 for evaporating the raw material used for the reaction, the combustor 13 for combusting the gas discharged from the fuel cell stack, and the raw material used for the reforming reaction using the heat of the combustion gas discharged from the combustor. In a steady state of the fuel cell system, the evaporation raw material is supplied from the first evaporator to the reforming system, and in a transient state where the required power generation amount to the fuel cell system increases, In addition to the evaporation material from the first evaporator, the evaporation material is supplied from the second evaporator to the reforming system, and the second evaporator makes up for the evaporation material from the first evaporator that is insufficient with respect to the required power generation amount. Reforming as Supply evaporative fuel to the system.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system mounted on a vehicle.

Conventionally, as a fuel cell system, heat exchange is performed between the hydrogen-rich reformed gas discharged from the reformer and water, and the water is heated up to a gas-liquid two-phase state. There is a technique for obtaining high reforming efficiency by using a carbon monoxide (hereinafter referred to as CO) selective oxidation section, that is, performing reaction heat recovery, maintaining a CO selective oxidation catalyst at a predetermined temperature (Patent Document 1). reference.). Further, in the fuel cell system, a combustion chamber and a starting combustion mechanism are provided upstream of the reformer, and the starting combustion mechanism is provided with an injector capable of supplying a reforming raw material. There is a technique that can be improved (see Patent Document 2).
JP 2002-47002 A JP 2000-63105 A

  However, since the invention described in Patent Document 1 evaporates the reforming raw material (water) by heat recovery of the reformed gas, when the load demand on the fuel cell system increases, the reformed gas from the upstream This is a configuration in which the reforming raw material can be increased for the first time only when there is an increase, and there is a problem that the response of the reformer is slow. Moreover, in the invention described in Patent Document 2, since fuel is burned immediately before the reformer and the heat quantity corresponding to the insufficient load change is compensated by the heat, the response is excellent, but the combustion efficiency is low. .

  In view of the above problems, an object of the present invention is to provide a fuel cell system that recovers heat in the reforming system, has high thermal efficiency, and has improved responsiveness to fluctuations in output load of the system. To do.

  The present invention relates to a fuel cell system including a fuel cell stack and a reforming system that supplies hydrogen-rich reformed gas to the fuel cell stack, and recovers heat generated in the reforming system to perform a reforming reaction. A first evaporator for evaporating the raw material used for the fuel, a combustor for burning the gas discharged from the fuel cell stack, and a first for evaporating the raw material used for the reforming reaction using the heat of the combustion gas discharged from the combustor. 2 evaporators, and in the steady state of the fuel cell system, the evaporation material is supplied from the first evaporator to the reforming system, and in the transient state where the required power generation amount to the fuel cell system increases, the first evaporator In addition to the evaporation material, the evaporation material is supplied from the second evaporator to the reforming system so as to compensate for the evaporation material that is insufficient with respect to the required power generation amount.

  According to the present invention, since the shortage of the steam raw material at the time of required load fluctuation is supplied from the second evaporator to the reforming system, the output responsiveness to the required load fluctuation can be improved and the drivability can be improved.

  FIG. 1 is a schematic view of a fuel cell system of the present invention.

  The reforming reactor 1 that generates the reformed gas is supplied with fuel in the fuel tank 2 (for example, hydrocarbon fuel such as methanol) from the first fuel flow path 31 via the fuel pump 3. Further, air is supplied to the reforming reactor 1 from the blower 4 serving as an air supply source through the first air channel 41 and the second air channel 42. The first heat exchanger 5 is installed at the connection portion between the first air flow path 41 and the second air flow path 42, and the air supplied to the reforming reactor 1 is converted into the reformed gas from the reforming reactor 1. Heat by heat exchange.

  Also, the steam from the first evaporator 6 is supplied to the reforming reactor 1 from the first water channel 51 and the second water channel 52. Since the water supplied from the first evaporator 6 passes through the first heat exchanger 5 described above, the water is heated by the reformed gas in the first heat exchanger 5 to become water vapor, and is reformed from the second water flow path 52. To the quality reactor 1.

  The first evaporator 6 will be described. The first evaporator 6 is integrally formed with the CO selective oxidation reactor 9, and the CO selective oxidation reactor 9 includes a reformed gas of about 300 ° C. from the shift reactor 10. Is supplied. After the CO selective oxidation treatment, the fuel cell stack 12 is supplied with a reformed gas of about 80 ° C. Heat based on this temperature difference (corresponding to 10 to 20 kW) is dissipated, this heat is transmitted to the first evaporator 6, and acts on the first water pump 8 through the third water channel 53 from the water tank 7. 1 The water flowing through the evaporator 6 is evaporated. Therefore, the first evaporator 6 generates steam by the reaction heat generated when the reformed gas is supplied to the CO selective oxidation reactor 9 and the sensible heat of the CO selective oxidation reactor 9 itself. Water vapor cannot be generated unless it is generated, and it takes time from the start to the generation of water vapor, or until the amount of water vapor corresponding to the changed required load from when the required load changes.

  The reformed gas discharged from the reforming reactor 1 passes through the first heat exchanger 5 installed in the middle of the first reformed gas channel 61 and flows into the shift reactor 10. The shift reactor 10 reacts CO in the reformed gas with water to generate hydrogen, thereby increasing the hydrogen concentration in the reformed gas and lowering the CO concentration in the reformed gas. The water used for this shift reaction is supplied from the water tank 7 to the shift reactor 10 through the fourth water channel 54 by the action of the second water pump 11.

  The reformed gas whose hydrogen concentration has been increased in the shift reactor 10 passes through the second reformed gas flow path 62 and flows into the CO selective oxidation reactor 9, while the CO selective oxidation reactor 9 enters the CO selective oxidation reactor 9 from the blower 4. A CO selective oxidation reaction is caused with the air supplied through the three air flow path 43 to reduce the CO in the reformed gas to a predetermined concentration. The reforming reactor 1 to the CO selective oxidation reactor 9 and the shift reactor 10 are referred to as a reforming system.

  The reformed gas whose CO concentration has decreased to a predetermined concentration is supplied from the third reformed gas channel 63 to the fuel cell stack 12. Air is supplied to the fuel cell stack 12 from the fourth air flow path 44 branched from the third air flow path 43, and power is generated using the reformed gas and air.

  The exhaust reformed gas that has not been used for power generation discharged from the fuel cell stack 12 is sent to the combustor 13 through the fourth reformed gas channel 64, and the fifth air channel branched from the first air channel 41. The high-temperature combustion gas generated by mixing and burning with the air supplied from 45 is sent to the second evaporator 14 through the first combustion gas passage 71.

  The water in the water tank 7 is supplied to the second evaporator 14 from the fifth water passage 55 branched from the fourth water passage 54. This water is sensible heat of the high-temperature combustion gas supplied from the combustor 13. Steam is generated by sensible heat of the second evaporator 14 itself, and is supplied to the reforming reactor 1 through the sixth water channel 56. The second evaporator 14 is provided with a pressure sensor 24 for detecting the internal pressure, and the detected pressure is sent to the integrated controller 20 for integrated control of the fuel cell system.

  Accordingly, there are two types of water supplied to the reforming reactor 1. First, the water supplied to the first evaporator 5 that is configured integrally with the CO selective oxidation reactor 9 is the CO selective. The water vapor evaporated by heat exchange with the CO selective oxidation reactor 9 heated by the oxidation reaction or heat of the reformed gas, and the second water vapor is supplied from the second evaporator 14.

  Since the second evaporator 14 can change water into steam using the high-temperature combustion gas supplied from the combustor 13, the time from the demand for load fluctuation to the generation of steam corresponding to the required load is The characteristics are shorter than those of the first evaporator 6.

  Specifically, the second evaporator 14 is provided with a pressure relief valve (pressure control valve) 99 (not shown) that variably controls the pressure of water vapor flowing through the second evaporator 14. Is installed at a branch point between the sixth water channel 56 and the eighth water channel 58. The pressure relief valve 99 controls the water vapor generated by the heat quantity of the combustion gas introduced into the second evaporator 14 in accordance with the water vapor temperature and pressure in the second evaporator 14. When the required power generation amount to the fuel cell system increases, the pressure relief valve 99 of the second evaporator 14 is opened, the pressure in the second evaporator is released to the eighth water flow path 58 connected to the water tank 7, and the second By reducing the pressure in the evaporator 14, the water in the second evaporator 14 is further boiled under reduced pressure, and water vapor is instantly generated, so that it is possible to respond quickly to load fluctuations.

  Moreover, by opening the pressure relief valve 99 during the generation of water vapor, the internal pressure of the second evaporator 14 is lowered, and the boiling point of water is lowered. Therefore, the heat of the housing of the second evaporator 14 can be efficiently used for water evaporation. For this reason, even if the combustion gas from the combustor 13 decreases, the production amount of water vapor can be maintained.

  When the required power generation amount to the fuel cell system shifts from the transient state to the steady state, the pressure relief valve 99 of the second evaporator 14 is closed to increase the internal pressure. By raising the internal pressure of the evaporator 14, the boiling point rises again, the heat of the housing of the second evaporator 14 can be efficiently transferred to water, and the amount of water is increased by transferring heat to water during steady operation. And it can be prepared for the next load fluctuation.

  The pressure relief valve 99 of the second evaporator 14 is controlled by the integrated controller 20, and the integrated controller 20 controls the amount of water vapor discharged from the pressure relief valve 99 according to the temperature and pressure in the second evaporator 14. . However, in a situation where the required power generation amount to the fuel cell system increases instantaneously and decreases, the second evaporator 14 cannot follow the required water vapor generation amount, and generates water vapor with a delay. The water vapor generated by the two evaporators 14 is excessively generated. In such a case, by controlling to release a predetermined amount of excess water vapor from the pressure relief valve 99 according to the temperature and pressure in the second evaporator 14, a predetermined amount of heat is generated in the second evaporator 14. The provided water vapor can be retained, the internal pressure does not become an overpressure, and the water vapor can be quickly released at the next water vapor release.

  Exhaust air that has not been used for power generation in the fuel cell stack 12 is supplied to the condenser 15 installed downstream of the second evaporator 14 through the sixth air flow path 46. Further, the combustion gas discharged from the second evaporator 14 is also supplied to the condenser 15 through the second combustion gas passage 72. The moisture in the gas is recovered by the condenser 15 and the gas is released to the outside. The condenser 15 that has recovered the moisture in the gas supplies the recovered water to the water tank 7 through the seventh water channel 57.

  A second heat exchanger 21 and a temperature sensor 22 for detecting the temperature of the gas discharged from the second heat exchanger 21 are installed between the second combustor 14 and the condenser 15, and the output of the temperature sensor 22. The signal is sent to the integrated controller 20. In the figure, reference numerals 91 to 95 denote flow rate control valves for controlling the flow rate of the fluid flowing through each flow path, and the opening degree is controlled by the integrated controller 20 according to the operating conditions of the fuel cell system.

  The electric power generated by the fuel cell stack 12 is supplied to the drive motor 17 via the inverter 16, and the drive motor 17 drives the drive wheels 18 with the required drive torque to run the vehicle. The drive motor 17 is driven by the power from the battery 19 as a secondary battery when the required drive torque cannot be generated by the power from the fuel cell stack.

  The battery 19 supplies power to the drive motor 17 so as to compensate for the shortage of the power generation amount of the fuel cell system with respect to the required power required for the target drive force of the vehicle, and the drive motor 17 delays the required drive torque with respect to the request. Drive torque is output without any problems. In the fuel cell system of the present invention, the power supply from the battery 19 to the drive motor 17 and the power generation state of the fuel cell stack 12 are controlled by the integrated controller 20.

  Hereinafter, the operation of the fuel cell system of the present invention will be described separately depending on whether or not the required load on the fuel cell stack 12 varies.

  In a steady running state in which the required load on the fuel cell stack 12 does not vary, the drive motor 17 can generate the required drive torque by the electric power generated by the fuel cell stack 12, and the electric power of the battery 19 is not used.

  Here, the operating state of the fuel cell system is such that moisture for generating the reformed gas necessary for generating the required amount of power generation in the fuel cell stack 12 is supplied to the reforming reactor 1 only from the first evaporator 6. It is sufficient to supply it, and it is not necessary to supply moisture from the second evaporator 14 to the reforming reactor 1.

  On the other hand, control when there is a change in the required load on the fuel cell system, for example, when shifting from the steady state to the acceleration state (when the load increases) will be described using the flowchart of FIG. 2 and the timing chart of FIG. The control of the flowchart of FIG. 2 is performed by the integrated controller 20 under predetermined conditions.

  First, in step 1 (S1 in FIG. 2, the same applies hereinafter), a power generation amount D2 (see FIG. 3) required for the fuel cell is read. A power amount ΔD to be increased is calculated from the difference between the power generation amount D2 and the current power generation amount D1. In step 2, the evaporation amount is determined from a steam generation curve showing the relationship between the load fluctuation and the evaporation amount as shown in FIG. 4 based on the calculated electric energy ΔD.

  As shown in FIG. 4, the steam generation curve is obtained by correcting the basic characteristic of the evaporation performance of the second evaporator 14 with respect to nonuniform temperature distribution in the second evaporator 14 and the high temperature flowing through the second evaporator 14. The characteristics of the evaporation amount are determined by performing correction based on the amount of fluid. In the fuel reforming type fuel cell system as in the present invention, it is the evaporation of water that controls the transient change. If the evaporation amount of water can be determined from the steam generation curve, the power generation amount of the fuel cell system Can be estimated.

  In the subsequent step 3, the output of the battery 4 is determined. The output characteristics of the battery 4 are determined so as to compensate for the difference between the required power generation amount for the fuel cell system and the power generation amount of the fuel cell system estimated in step 2.

  In step 4, water vapor is generated based on the evaporation amount of the second evaporator 14 calculated in step 2 and step 3 and the output of the battery 4, and electric power is output. On the other hand, in step 5, electric power is output from the battery 4 based on the battery 4 output calculated in step 3. The second evaporator 14 opens the pressure relief valve 99 and releases the pressure in the second evaporator 14 to the water tank through the eighth water flow path 58. Thus, steam is generated by lowering the internal pressure P in the second evaporator 14 from the predetermined pressure P2 on the high pressure side (for example, 3 atmospheres) to the predetermined pressure P1 on the low pressure side (for example, atmospheric pressure). Since the generation of water vapor supplied from the second evaporator 14 necessary for generating the required power generation amount is delayed, first, the electric power from the battery 4 is supplied to the drive motor 17 and is generated by the second evaporator 14 with a delay. When the power generation in the fuel cell stack 12 by the steam is started, the power supplied from the battery 4 is controlled to decrease.

  In step 6 following step 4, the target vapor amount of the first evaporator 6 corresponding to the electric energy ΔD calculated in step 1 in a state where the generation of vapor from the second evaporator 14 is continued is shown in FIG. It is determined based on the steam generation curve as shown in

  Generation of steam in the first evaporator 6 is started based on the amount of steam in the first evaporator 6 calculated in step 6 (step 8). On the other hand, in step 7 following step 6, the amount of steam generated in the second evaporator 14 is reduced in accordance with the amount of evaporation generated in the first evaporator 6.

  In step 9, when the amount of steam generated by the first evaporator 6 reaches the target steam amount, the generation of steam in the second evaporator 14 is stopped.

  In subsequent step 10, it is determined that the state of the fuel cell system is in a steady state. If the fuel cell system is in a steady state, the process proceeds to step 11;

  In step 11, the internal pressure of the second evaporator 14 is increased to a predetermined pressure P2, and the control is finished. By increasing the internal pressure of the second evaporator 14, water vapor can be generated quickly at the next load fluctuation.

  Next, using the timing chart of FIG. 3, the contents of control when the load changes according to the present invention will be described.

  First, until time t1, the power generation amount D1 is in a steady running state, and at time t1, the required power generation amount changes from D1 to D2 on the high load side. Then, the output of the battery 4 increases almost at the same time as the fluctuation of the required power generation amount. The output of the battery 4 is an output corresponding to the required power generation amount.

  At time t2, the internal pressure of the second evaporator 14 is reduced from P2 to P1, and generation of water vapor is started. The output from the battery 4 decreases corresponding to the increase in the amount of water vapor generated from the second evaporator 14. Note that the sum of the power generation amount of the fuel cell stack 12 by the water vapor from the second evaporator 14 and the output from the battery 4 matches the required power generation amount.

  At time t3, the reforming reaction is promoted with the steam from the second evaporator 14, the heat generation of the CO selective oxidizer 9 increases, and the amount of water vapor generated in the first evaporator 6 increases with the increase in heat generation. Begin to. As the amount of water vapor generated from the first evaporator 6 increases, the amount of water vapor generated in the second evaporator 14 decreases. At this time, the power generation amount as the total amount of water vapor from the first evaporator 6 and water vapor from the second evaporator 14 corresponds to the required power generation amount. Then, at time t4, the amount of water vapor from the second evaporator 14 becomes the maximum amount, and thereafter decreases as the amount of water vapor from the first evaporator 6 increases. Note that the output of the battery 4 decreases as the amount of water vapor generated by the second evaporator 14 increases and becomes substantially zero by time t4.

  At time t5, the generation of water vapor in the second evaporator 14 is stopped, the pressure relief valve is closed, the internal pressure is increased to P2, and the required power generation amount is obtained only by the generation amount of water vapor from the first evaporator 6. It maintains, and it transfers to the steady state with the electric power generation amount D2.

  The water vapor temperature of the second evaporator 14 is lowered because the sensible heat of the combustion gas and the sensible heat of the second combustor 13 are consumed for the production of water vapor in the second evaporator 14. is there.

  For control when there is a change in the required load on the fuel cell system, for example, when shifting from a steady state to a deceleration state (when the load decreases), the power generation amount supplied from the fuel cell system with respect to the required power generation amount Therefore, it is necessary to consume surplus power. For example, the surplus power may be stored in the battery 4 or consumed by a motor in a power running state.

  As described above, the present invention provides a fuel cell system including a reforming system that supplies hydrogen-rich reformed gas to a fuel cell stack, and recovers heat generated in the reforming system to be used for a reforming reaction. The first evaporator 6 for evaporating the gas, the combustor 13 for combusting the gas discharged from the fuel cell stack, and the raw material used for the reforming reaction using the heat of the high-temperature combustion gas discharged from the combustor And a second evaporator 14 that evaporates. In a steady state of the fuel cell system, the evaporation material is supplied from the first evaporator 6 to the reforming system, and the required power generation amount to the fuel cell system increases. In the state, in addition to the evaporation raw material from the first evaporator 6, the evaporated fuel is supplied from the second evaporator to the reforming system, and the second evaporator 14 is supplied from the first evaporator which is insufficient with respect to the required power generation amount. Evaporative fuel Supplying vaporized fuel to the reforming system to compensate.

  Therefore, at the time of steady operation of the fuel cell system, since the evaporation material is supplied to the reforming system using the first evaporator 6 that evaporates the reforming material using the heat generated in the reforming system, the thermal efficiency of the fuel cell system is improved. Can be improved. On the other hand, when the load increases, the amount of evaporation material supplied from the first evaporator is delayed with respect to the amount of evaporation material that generates the required power generation amount. Therefore, the generation amount corresponding to the required power generation amount is delayed. Occurs. By compensating for the shortage due to this delay with the supply of the evaporation raw material from the second evaporator 14, the delay in the generation of the power generation amount corresponding to the required power generation amount is suppressed, and the output responsiveness of the reforming system with respect to the load fluctuation request Can improve drivability.

  Further, in the present invention, the reforming system is provided with the CO selective oxidation reactor 9, and the first evaporator has the reaction heat generated in the CO selective oxidation reactor 9 and the reformed gas supplied to the CO selective oxidation reactor 9. The raw material (water) was evaporated using sensible heat. Here, the CO selective oxidation reactor 9 is usually arranged on the downstream side of the shift reactor 10 as shown in FIG. The reformed gas at about 300 ° C. discharged from the shift reactor 10 flows into the CO selective oxidation reactor 9. On the other hand, after the selective oxidation treatment of CO is performed, the reformed gas finally reaches about 80 ° C. and is supplied to the fuel cell stack 12. Although depending on the configuration of the fuel cell system, heat of about 10 to 20 kW is released in a series of flows of the reforming system, and an evaporation raw material is generated by the first evaporator 6 using this heat. As described above, since the evaporation raw material is generated in the first evaporator 6 using the heat generated in the CO selective oxidation reactor 9, a fuel cell system with high thermal efficiency can be obtained.

  FIG. 5 is a flowchart of an example of control content of the second heat exchanger 21 installed downstream of the second combustor 14.

  The operating state of the fuel cell system is such that the amount of combustion gas in the combustor 13, the housing of the second evaporator 14, and the water stored in the second evaporator 14 according to changes in required power in transient and steady states. The amount of heat is different. In particular, when the fuel cell system continues to operate for a long time under a high load, the amount of heat of the combustion gas is not consumed in the second evaporator 14, and flows into the combustion gas in a temperature range that cannot flow through the condenser 15 as it flows downstream. There is a possibility. The temperature control of the combustion gas using the second heat exchanger 21 installed downstream of the second evaporator 14 in this case will be described.

  First, in step 21, the combustion gas temperature T at the outlet of the second heat exchanger 21 is measured by the temperature sensor 22. Next, it is determined whether the detected temperature T is equal to or higher than the processable temperature upper limit value Te2 of the capacitor 15 (step 22). If it is equal to or higher than Te2, an appropriate medium such as oil flowing through the second heat exchanger 21 is circulated. Then, heat exchange is performed between the medium and the combustion gas to lower the temperature of the combustion gas (step 23). If the temperature of the combustion gas is less than Te2 in step 22, the process returns to step 21 and the temperature detection is repeated. In step 24 following step 23, the detected temperature T is compared with the processing switching temperature Te1 of the capacitor 15 (where Te1 <Te2), and the detected temperature T becomes equal to or lower than the processing switching temperature Te1 of the capacitor 15. Then, the circulation of the medium of the second heat exchanger 21 is stopped (step 25), and the process returns to the first step. If the process switching temperature Te1 is exceeded, the temperature determination in step 24 is repeated.

  By controlling the second heat exchanger 21 as described above, the combustion gas flowing into the condenser 15 by the second heat exchanger 21 even in a state where the fuel cell system continues the high load steady operation for a long time. The temperature can be appropriately controlled, and the moisture in the combustion gas can be efficiently recovered by the capacitor 15.

  FIG. 6 is a diagram showing a configuration of a fuel cell system as a second embodiment of the present invention. This configuration is different from the configuration of the first embodiment in that a second fuel flow path 32 that supplies fuel from the fuel tank 2 to the combustor 13 is installed in the middle of the second fuel flow path 32, and the fuel is A fuel pump 23 for supplying to the combustor 13 was added. Furthermore, an eighth water channel 58 for branching from the sixth water channel 56 for supplying water vapor from the second evaporator 14 to the reforming reactor 1 and discharging the water vapor to the water tank 7, an existing water tank 7, A ninth water channel 59 branched from the fifth water channel 55 connecting the second evaporator 14 and connected to the eighth water channel 58 is installed. Further, a tenth water channel 60 that branches from the sixth water channel 56 that supplies the steam of the second evaporator 14 to the reforming reactor 1 and supplies the steam to the shift reactor 10, and the pressure in the second evaporator 14. Is added to the pressure sensor 24. The output of the pressure sensor 24 is output to the integrated controller 20.

  A flow rate control valve 96 is installed at the branch point between the fifth water channel 55 and the ninth water channel 59, and a flow rate control valve 98 is installed at the branch point between the eighth water channel 58 and the ninth water channel 59. Is done. A flow control valve 97 is also installed at the branch point between the sixth water channel 56 and the tenth water channel 60. A pressure relief valve 99 is installed at a branch point between the sixth water channel 56 and the eighth water channel 58 in the second evaporator 14, and these valves are controlled by the integrated controller 20.

  With this configuration, the control contents of this embodiment will be described with reference to FIG. This control is performed by the integrated controller 20. This control is a control for dealing with the case where the water vapor generated by the second evaporator 14 becomes excessive depending on the operating conditions of the fuel cell system, and this excessive water vapor is generated.

  First, in step 31, the internal pressure P of the second evaporator 14 is read from the pressure sensor 24. Subsequently, at step 32, it is determined whether or not the detected internal pressure P is equal to or higher than a predetermined pressure PL2 of the second evaporator 14, and if it is equal to or higher than PL2, the process proceeds to step 33 and the internal pressure P of the second evaporator 14 is decreased. Therefore, the flow control valve 98 and the pressure relief valve 99 are switched, and the water vapor discharged from the second evaporator 14 is released to the water tank 7 through the water channel 57. When the detected internal pressure P is less than PL2, the process returns to step 31, and the detection of the internal pressure P of the second evaporator 14 is repeated.

  In step 34 following step 33, the internal pressure in the second evaporator 14 is again detected and read using the pressure sensor 24, and in step 35, the detected internal pressure is changed to a predetermined pressure PL1 (here, the second evaporator 14). , PL1 <PL2). If the detected internal pressure is less than or equal to the predetermined pressure PL1, the flow control valve 98 and the pressure relief valve 99 switched in step 33 are returned to the original state (step 36), and if the predetermined pressure PL1 is exceeded, the process returns to step 34. The internal pressure of the second evaporator 14 is detected again.

  By setting it as such control, the water vapor pressure in the 2nd evaporator 14 can be maintained appropriately, and failure of the 2nd evaporator 14 can be prevented.

  In the above description, the method of lowering the pressure in the second evaporator 14 by discharging excess water vapor has been described. However, when the fuel cell system is stopped, the second evaporator 14 itself has heat. Therefore, the flow control valves 96 and 98 may be switched so that the water vapor in the second evaporator 14 is discharged from the fifth water channel 55 to the water tank 7 through the water channels 59 and 58.

  The flowchart shown in FIG. 8 is modified according to the temperature and amount of steam when supplying steam from the second evaporator 14 to the reforming reactor 1 (for example, in an accelerated running state where the load increases from a steady state). The correction of the amount of air and the amount of fuel supplied to the quality reactor 1 will be described. This control can be applied to each of the first and second embodiments.

  First, at step 41, the required power for generating the required driving force is read, and the power corresponding to the load fluctuation is calculated. Next, at step 42, a steam generation curve of the second evaporator 14 is calculated based on the fluctuation power. The temperature and amount of water vapor generated from this steam generation curve are obtained, and the correction amount of air and fuel supplied to the reforming reactor 1 is calculated taking into account the activation temperature of the reforming reactor 1 (step 43). The amount of air and the amount of fuel at this time are corrected so that the temperature of the steam supplied to the reforming reactor 1 becomes the activation temperature of the reforming reactor 1. In step 44, the blower 4 and the fuel pump 3 are controlled so that the air amount and the fuel amount with the calculated corrected air amount and the corrected fuel amount are taken into account.

  As described above, when the steam generated in the second evaporator 14 is supplied to the reforming reactor 1, the steam is heated so that the steam temperature becomes the activation temperature of the reforming reactor 1. Correct the amount of air and fuel supplied. For this reason, there is no waste in the amount of heat for heating the supplied water vapor, and the thermal efficiency can be improved.

  As shown in the second embodiment of FIG. 6, the water vapor from the second evaporator 14 may be additionally supplied from the sixth water channel 56 to the shift reactor 10 through the tenth water channel 60.

  In fuel reforming, water is mainly consumed by the reforming reactor 1 and the shift reactor 10. Therefore, by making it possible to supply the steam generated in the second evaporator 14 to the reforming reactor 1 and the shift reactor 10, it is possible to prevent water shortage in these reactors. In particular, when water shortage occurs in the reforming reactor 1, carbon deposition occurs and the reforming efficiency decreases, and it is important to prevent it.

  The flowchart shown in FIG. 9 shows that when the vehicle equipped with the fuel cell system is in a steady running state and the steam supplied to the reforming reactor 1 is insufficient, the steam from the second evaporator 14 is reformed. The contents of the control when supplying to 1 to compensate for the shortage will be described.

  First, in step 51, the temperature and humidity of air supplied to the reforming reactor 1 are read from the sensor 25 installed at the inlet of the reforming reactor 1. In step 52, the detected temperature and humidity of the air are compared with basic values of the temperature and humidity of the air set in advance in the reforming reactor 1, and the difference F in the amount of water contained in the air is calculated from the difference. .

  In step 53, the difference F in water amount is subtracted from the steady discharge amount of the water pump 11 that supplies water to the second evaporator 14, and in step 54, it is determined whether or not the value D is within a predetermined range. If this value D is less than or equal to the predetermined range, the amount of moisture in the air is large, and the discharge amount of the water pump 11 is reduced, in other words, the amount of water vapor generated by the second evaporator 14 is reduced (step 55). ). Moreover, if it is in the predetermined range, the water | moisture content in air is equivalent to the set moisture content, and the discharge amount of the water pump 11 is maintained (step 56). On the other hand, if it is more than the predetermined range, the amount of moisture in the air is less than the set amount, the amount of water generated by the second evaporator 14 is adjusted by increasing the discharge amount of the water pump 11 and adjusting the amount of moisture. Increase (step 57).

  Therefore, the humidity conditions of the air used in the partial oxidation reaction and autothermal reaction, especially the air supplied from the outside air, change every time it is supplied, and this change in humidity affects the conditions of the reforming reaction. However, by making it possible to supply the steam of the second evaporator 14 even in a steady state, the amount of water supplied to the reforming reactor is controlled to a predetermined amount using the steam from the second evaporator 14. Thus, the reforming conditions can be made constant and the reforming can be performed more efficiently.

  In this way, the amount of water vapor supplied from the second evaporator 14 to the reforming reactor 1 is corrected by the amount of moisture in the air supplied to the reforming reactor 1, so that the reforming reactor 1 can be more accurately specified. The amount of water supplied can be controlled within an optimal range, the reforming efficiency can be improved, and the reforming reactor 1 can be prevented from being deteriorated due to water shortage.

  In the above description, the amount of water in the air supplied to the reforming reactor 1 is detected to correct the amount of water vapor supplied from the second evaporator 14, but the amount of water in the air outside the fuel cell system is corrected. The same effect can be obtained by correcting the amount of water vapor supplied from the second evaporator 14 based on the above.

  In addition, this invention is not limited to said Example and embodiment. For example, when the second evaporator 14 continues compensation by supplying water vapor when the load fluctuates, the amount of heat of the second evaporator 14 itself decreases, or when the fuel cell system continues in an idle state, the second evaporator 14 As shown in the system diagram of FIG. 6, the second fuel flow path 32 and the fuel pump 23 are provided from the fuel tank 2. Since air is supplied to the combustor 13 from the fifth air flow path 45, additional fuel may be burned in the combustor 13 and the heat amount of the second evaporator 14 may be maintained.

  In addition, the evaporation of water that controls the responsiveness of the fuel cell system among the evaporation materials has been described so far. However, the evaporation material may be a fuel.

  It is also conceivable that the fuel reforming S / C (the ratio of water to the amount of fuel) should be greatly increased. In this case, the water vapor ratio for the transient compensation control shown in FIG. 2 and the steady compensation control shown in FIG. 9 of the second evaporator 14 may be set freely, for example, by increasing the ratio for steady compensation control.

  In addition, the temperature of the combustion gas is finally lowered by the condenser 15 and water is recovered, but a system that humidifies the air used as the oxidizing gas of the reforming and fuel cell stack using the cooling medium at this time can also be used. good.

  In addition, the autothermal reforming system has been described here, but the same effect can be obtained with a plasma reforming system.

  The fuel cell system to which the present invention is applied can supply the required power when the load fluctuates, and thus can be used for a vehicle or the like that particularly requires responsiveness.

It is a block diagram of the fuel cell system of this invention. It is a flowchart explaining the control content of this invention. It is a timing chart explaining the contents of control of the present invention. It is a figure which shows an example of a steam generation curve. It is a flowchart explaining the control content of a 2nd heat exchanger. It is a block diagram of the fuel cell system of 2nd Embodiment. It is a flowchart which shows the control content of 2nd Embodiment. It is a flowchart explaining correction | amendment of the air quantity and fuel quantity which are supplied to a reforming reactor. FIG. 6 is a flowchart for explaining the control contents when supplying the steam to the reforming reactor from the second evaporator to compensate for the shortage when the steam to be supplied to the reforming reactor becomes insufficient in the steady running state. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming reactor 2 Fuel tank 3 Fuel pump 4 Blower 5 1st heat exchanger 6 1st evaporator 7 Water tank 8 Water pump 9 CO selective oxidizer 10 Shift reactor 11 Water pump 12 Fuel cell stack 13 Combustor 14 4th evaporator 15 capacitor | condenser 16 inverter 17 drive motor 18 drive wheel 19 battery 20 integrated controller 21 2nd heat exchanger 22 temperature sensor 24 pressure sensor 31-33 1st-3rd fuel flow path 41-46 1st-6th Air channels 51 to 59 First to ninth water channels 61 to 64 First to fourth reformed gas channels 71, 72 First and second combustion gas channels 99 Pressure relief valve

Claims (13)

A fuel cell stack;
A reforming system for supplying hydrogen-rich reformed gas to the fuel cell stack;
In a fuel cell system comprising:
A first evaporator for recovering heat generated in the reforming system and evaporating a raw material used for the reforming reaction;
A combustor for burning the gas discharged from the fuel cell stack;
A second evaporator that evaporates the raw material used for the reforming reaction using the heat of the combustion gas discharged from the combustor,
In a steady state of the fuel cell system, the evaporation material is supplied from the first evaporator to the reforming system,
In a transient state in which the required power generation amount to the fuel cell system increases, in addition to the evaporation raw material from the first evaporator, the evaporation raw material that is insufficient with respect to the required power generation amount from the second evaporator is compensated. A fuel cell system that supplies an evaporation material to a reforming system. The reforming system includes a carbon monoxide selective oxidizer,
2. The fuel cell system according to claim 1, wherein the first evaporator evaporates the raw material using the reaction heat in the carbon monoxide selective oxidizer and the sensible heat of the reformed gas.   2. The fuel cell system according to claim 1, wherein the pressure of the raw material flow path in the second evaporator is controlled.   4. The fuel cell system according to claim 3, wherein when the required power to the fuel cell system increases, the pressure in the second evaporator is reduced.   5. The fuel cell system according to claim 4, wherein when the required power to the fuel cell system changes from an increase to a constant, the pressure in the second evaporator is increased. A condenser for recovering moisture in the combustion gas discharged from the second evaporator;
A heat exchanger for controlling the temperature of the combustion gas discharged from the second evaporator,
The fuel cell system according to any one of claims 1 to 5, wherein the heat exchanger controls a temperature of a combustion gas flowing into the condenser to a predetermined temperature. The second evaporator comprises a pressure control valve;
4. The fuel cell system according to claim 3, wherein the pressure control valve controls the amount of raw material discharged from the pressure suppression control valve in accordance with a raw material temperature or a raw material pressure in the second evaporator. The reforming system includes:
A reforming reactor that reforms the fuel into a hydrogen-rich reformed gas;
A water gas shift reactor that reduces the carbon monoxide contained in the reformed gas and increases the hydrogen concentration in the reformed gas;
The second evaporator is an evaporator that converts water into water vapor,
The fuel cell system according to claim 3, wherein water vapor generated in the second evaporator is supplied to at least one of the reforming reactor and the water gas shift reactor.   9. The amount of air and fuel supplied to the reforming reactor is corrected according to the temperature and amount of water vapor supplied from the second evaporator to the reforming reactor. The fuel cell system described. A fuel cell stack;
A reforming system for supplying hydrogen-rich reformed gas to the fuel cell stack;
In a fuel cell system comprising:
A first evaporator for recovering heat generated in the reforming system and evaporating a raw material used for the reforming reaction;
A combustor for burning the gas discharged from the fuel cell stack;
A second evaporator that evaporates the raw material used for the reforming reaction using the heat of the high-temperature combustion gas discharged from the combustor,
When the fuel cell system is in a power generation state, in addition to the evaporation material from the first evaporator, the evaporation material is supplied from the second evaporator so as to supplement the evaporation material that is insufficient with respect to the required power generation amount. A fuel cell system for supplying to a reforming system. It has a sensor that detects the temperature and humidity of the outside air,
The second evaporator is an evaporator that converts water into water vapor,
11. When the fuel cell system supplies water vapor from the second evaporator to the reforming system during steady operation, the amount of water vapor supplied is corrected according to the detected outside air temperature and humidity. The fuel cell system described in 1. A sensor for detecting the temperature and humidity of the air supplied to the reforming system;
The second evaporator is an evaporator that converts water into water vapor,
11. When the fuel cell system supplies steam from the second evaporator to the reforming system during steady operation, the amount of steam supplied is corrected according to the detected air temperature and humidity. The fuel cell system described in 1. A drive motor using a fuel cell stack and a reforming system that supplies hydrogen-rich reformed gas to the fuel cell stack, and a battery that stores electric power generated by the fuel cell. In a fuel cell vehicle driven by
The fuel cell system includes:
A first evaporator for recovering heat generated in the reforming system and evaporating a raw material used for the reforming reaction;
A combustor for burning the gas discharged from the fuel cell stack;
A second evaporator that evaporates the raw material used for the reforming reaction using the heat of the high-temperature combustion gas discharged from the combustor,
In a steady state of the fuel cell system, the evaporation material is supplied from the first evaporator to the reforming system,
In a transient state in which the required power generation amount to the fuel cell system increases, in addition to the evaporation raw material from the first evaporator, the evaporation raw material that is insufficient with respect to the required power generation amount from the second evaporator is compensated. A fuel cell vehicle characterized in that evaporative fuel is supplied to a reforming system, and the battery supplies power to the drive motor so as to compensate for a shortage of power generation amount of the fuel cell stack with respect to the required power generation amount. .

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