WO2014006988A1 - Fuel cell generation system, and method of controlling fuel cell generation system - Google Patents

Abstract

A fuel cell generation system is provided with: an air-heating heat exchanger (13) disposed on the output side of an air blower (12) that heats air (oxidation gas) delivered by the air blower (12) by causing the air to be passed toward a low-temperature flow passage; and a combustion burner (23) disposed downstream of the air-heating heat exchanger (13) that further heats the oxidation gas heated by the air-heating heat exchanger (13) before supplying the oxidation gas to a cathode electrode (11a) of a fuel cell (11).

Description

Fuel cell power generation system and control method for fuel cell power generation system

The present invention relates to a fuel cell power generation system that generates power by adjusting the temperature of a fuel cell according to a power output request, and a control method for the fuel cell power generation system.

Conventionally, a solid oxide fuel cell (SOFC) has been known as a highly efficient fuel cell, and in recent years, it has been studied to install a SOFC in a vehicle. When an SOFC is used for a vehicle, load fluctuations frequently occur. Therefore, when compared with a stationary SOFC, it is necessary to perform a flexible output change corresponding to the load fluctuations. For this reason, it is necessary to stabilize the power generation reaction of SOFC in a short time. Conventionally, a technique disclosed in Japanese Patent Laid-Open No. 2003-115315 has been proposed.

In the fuel cell power generation system disclosed in the above-mentioned patent document, the heat exchanger and the combustion burner are arranged in series on the upstream side of the fuel cell, and the combustion burner is arranged on the upstream side of the heat exchanger. It is configured. For this reason, the gas burned by the combustion burner flows into the heat exchanger provided on the downstream side, so that some of the combustion gas components, such as unburned fuel, adhere and accumulate inside the heat exchanger, and heat exchange There is a problem that performance decreases. In addition, there is a problem that moisture in the combustion gas is condensed inside the heat exchanger when starting and stopping, and corrosion inside the heat exchanger due to this is generated.

The present invention has been made to solve such a conventional problem, and the object of the present invention is to stably change the power generation output without causing a decrease in performance or deterioration of the heat exchange means. It is to provide a fuel cell power generation system capable of achieving the above.

In order to achieve the above object, the present invention is provided on the output side of the oxidant gas supply means, and passes the oxidant gas to the low-temperature channel side, thereby heating the oxidant gas, and downstream of the heat exchange means. And a combustion burner provided on the side and further heating the oxidizing gas after being heated by the heat exchanging means and supplying it to the cathode electrode.

FIG. 1 is a block diagram showing the configuration of the fuel cell power generation system according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram showing a detailed configuration of the combustion burner of the fuel cell power generation system according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the fuel cell power generation system according to the second embodiment of the present invention. FIG. 4 is an explanatory diagram showing a detailed configuration of the combustion burner of the fuel cell power generation system according to the second embodiment of the present invention.

[Description of First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a fuel cell power generation system 100 according to the first embodiment of the present invention.

As shown in FIG. 1, the fuel cell power generation system 100 according to the first embodiment includes a fuel cell 11 having a cathode electrode 11a and an anode electrode 11b, and an air blower that supplies air (oxidizing gas) to the cathode electrode 11a. 12 (oxidizing gas supply means), an air heating heat exchanger 13 (heat exchange means) for heating air sent from the air blower 12, and a first fuel pump 14 (fuel) for sending fuel such as hydrocarbon fuel And a fuel reformer that reforms the fuel sent from the first fuel pump 14 via the fuel gas flow path Ll and supplies the generated reformed gas to the anode 11b of the fuel cell 11. 15. In the present embodiment, air is used as an example of the oxidizing gas, but is not limited to air, and a gas containing oxygen can be used.

Further, a fuel circulation blower 17 that circulates the fuel gas (anode off gas) discharged from the anode 11b to the fuel reformer 15, and an exhaust gas (cathode off gas) discharged from the cathode 11a are the exhaust gas flow path L2. Is provided between the output port of the fuel circulation blower 17 and the exhaust gas flow path L2, and is provided between the reformer heater 16 for heating the fuel reformer 15 with the introduced exhaust gas, and the anode The fuel gas pressure adjusting valve 18 for introducing a part of the fuel gas discharged from the electrode 11b into the exhaust gas flow channel L2, and the exhaust gas flow channel L2 in the vicinity of the inlet of the reformer heater 16 are provided. And an exhaust passage pressure adjusting valve 19 for discharging a part of the exhaust gas introduced into the reformer heater 16 via the gas passage L2 to the outside.

Further, air supplied from the air blower 12 and heated by the air heating heat exchanger 13 and air heated by combustion with the fuel supplied from the second fuel pump 22 are introduced into the oxidizing gas supply port of the cathode 11a. A combustion burner 23 is provided. The detailed configuration of the combustion burner 23 will be described later.

The fuel cell 11 is, for example, a solid oxide fuel cell (SOFC), and generates electric power by using a reformed gas supplied to the anode electrode 11b and air supplied to the cathode electrode 11a. Supplied to power demand equipment (not shown) such as a motor.

The fuel reformer 15 is heated by the heat supplied from the reformer heater 16 and reforms the fuel supplied from the first fuel pump 14 using a catalytic reaction. Then, the reformed fuel containing hydrogen gas is supplied to the anode 11b of the fuel cell 11.

Further, the air blower 12, the first fuel pump 14, the second fuel pump 22, the exhaust passage pressure adjustment valve 19, the fuel passage pressure adjustment valve 18, the fuel circulation blower 17, and the air flow rate control valve 25 are respectively controlled by a control unit. 31 (control means). The control unit 31 is, for example, a device including a central processing unit (CPU), a storage unit such as a RAM, a ROM, various operators, and a hard disk, and sends control signals to each device in response to a power output request. Send and control each device.

Next, the configuration of the combustion burner 23 will be described with reference to FIG. As shown in FIG. 2, the combustion burner 23 includes a front-stage combustor 23a that produces a small amount of combustion gas, and a rear-stage combustor 23b that burns a larger amount of fuel and air using the combustion gas of the front-stage combustor 23a. And.

Burner fuel is supplied from the fuel injection valve 26a to the pre-stage combustor 23a, and a part of the air heated by the air heating heat exchanger 13 (see FIG. 1) is distributed by the air flow control valve 25. Supplied. On the other hand, burner fuel is also supplied from the fuel injection valve 26b to the post-stage combustor 23b, and a part of the air heated by the air heating heat exchanger 13 is distributed by the air flow control valve 25 to be secondary. It is structured to be supplied as air. Then, the combustion gas generated by the combustion is output to the cathode 11a shown in FIG.

Next, the operation of the fuel cell power generation system 100 according to this embodiment will be described. The fuel cell power generation system 100 according to this embodiment changes the operating temperature of the fuel cell 11 by driving the combustion burner 23 and supplying heated air to the fuel cell 11, and the output power of the fuel cell 11. To respond to changes. Further, the combustion burner 23 is driven to start the system.

First, air is sent out from the air blower 12 by driving the air blower 12 shown in FIG. The air sent out from the air blower 12 passes through the low temperature side of the air heating heat exchanger 13, that is, the side that absorbs heat, and is then introduced into the combustion burner 23, and then into the oxidizing gas supply port of the cathode electrode 11a. be introduced. At this time, the gas discharged from the reformer heater 16 is introduced to the high temperature side of the air heating heat exchanger 13, that is, the side from which heat is released. Therefore, the air sent from the air blower 12 is heated to a temperature lower by about 200 ° C. to 300 ° C. than the temperature of the fuel cell 11 by the heat of the exhaust gas discharged from the reformer heater 16, and the combustion burner 23 To be introduced.

The air supplied to the combustion burner 23 is adjusted by the combustion burner 23 according to the operating state of the fuel cell 11, and then introduced into the oxidizing gas supply port of the cathode 11a.

When the gas temperature introduced into the oxidizing gas supply port of the cathode electrode 11 a is heated to a temperature higher than the outlet temperature of the air heating heat exchanger 13, the second fuel pump 22 is driven and the fuel is burned by the combustion burner 23. Fuel is supplied from the injection valve 26a and burned.

The temperature at that time is supplied to the front-stage combustor 23a and the rear-stage combustor 23b by adjusting the fuel supply amount by the fuel injection valves 26a and 26b, adjusting the air supply amount by the air blower 12, and by the air flow rate control valve 25. By adjusting the amount of air, the desired amount of air can be introduced into the oxidizing gas supply port of the cathode electrode 11a. Therefore, by controlling the combustion in the combustion burner 23 under the control of the control unit 31, the amount of air supplied to the fuel supply port of the cathode electrode 11a and the air temperature can be adjusted, and the power generation reaction can be performed in a short time. Can be stabilized.

Next, the relationship between the operating temperature of the fuel cell 11 and the power generation output will be described. First, the case where the fuel cell power generation system 100 is in an operating state will be described. The temperature of the air introduced into the oxidizing gas supply port of the cathode electrode 11a is, for example, 200 ° C. to 300 ° C. lower than the normal operating temperature of the fuel cell 11 (650 ° C. to 750 ° C.). For this reason, the air introduced into the cathode electrode 11a is heated by the thermal energy generated at the time of power generation of the fuel cell 11, reaches a temperature substantially the same as the temperature of the fuel cell 11, and is discharged from the outlet of the cathode electrode 11a.

And when the power output of the fuel cell 11 increases as the power consumption of the load increases, the amount of heat dissipated in the fuel cell 11 increases. In the fuel cell 11, if the amount of heat dissipation increases beyond the amount of heat that can be transferred to the air, the operating temperature of the fuel cell 11 rises and exceeds the normal operating temperature. In order to suppress this temperature rise, the output of the air blower 12 is controlled to increase the amount of air introduced into the oxidizing gas supply port of the cathode electrode 11a. That is, by increasing the amount of air, the amount of heat that can be transferred from the fuel cell 11 to the air can be increased, and as a result, the operating temperature of the fuel cell 11 can be lowered to a normal temperature.

Next, the combustion burner 23 is driven to appropriately adjust the outlet temperature of the combustion burner 23 and the flow rate of the heated gas sent from the combustion burner 23 with respect to the air sent from the air blower 12. An operation for changing the operating temperature of the battery 11 will be described.

When the air sent out from the air blower 12 is heated by the air heating heat exchanger 13, it is branched into two systems by the air flow rate control valve 25. Of these, the air in the first branch path is the preceding stage shown in FIG. Supplied to the combustor 23a, the air in the second branch path is supplied as secondary air to the subsequent combustor 23b. The front stage combustor 23a is supplied with fuel from the fuel injection valve 26a and burns, and the rear stage combustor 23b is supplied with fuel from the fuel injection valve 26b and burns.

At this time, the air flow rate control valve 25 controls the air temperature at the outlet of the combustion burner 23 by appropriately adjusting the amount of air supplied to the front stage combustor 23a and the amount of air supplied to the rear stage combustor 23b. The temperature of the fuel cell 11 is changed. When the temperature to be raised is small, the fuel supply amount to the fuel injection valve 26a and the air supply amount to the pre-stage combustor 23a may be small. When the temperature rise is high, it is necessary to increase both the fuel supply amount to the fuel injection valve 26a and the air supply amount to the pre-stage combustor 23a. At that time, it may be necessary to control the amount of air by the air blower 12 so that the amount of oxygen in the air introduced into the oxidizing gas supply port of the cathode electrode 11a can secure the amount necessary for power generation.

When starting up the system that requires the highest temperature rise in the system, the maximum allowable fuel is supplied to both the front-stage combustor 23a and the rear-stage combustor 23b. Combustion takes place. Since the temperature of the air supplied from the air heating heat exchanger 13 is low at the initial stage of starting the system, at the time of starting the front stage combustor 23a, ignition and combustion are maintained, and fuel is evaporated from the rear stage combustor 23b. The heating of the fuel and the heating of the air using the external energy is required for a short time.

Thereafter, the temperature of the fuel cell 11 and the reformer heater 16 provided downstream of the combustion burner 23 is gradually increased by the heated gas delivered from the combustion burner 23, and the air heating heat exchanger 13 is supplied to the air heating heat exchanger 13. The exhaust gas temperature to be supplied rises. Along with this, the temperature of the air delivered from the air blower 12 at the outlet of the air heating heat exchanger 13 also rises, so that it is not necessary to heat the fuel and air used for the combustion burner 23 using external energy. The sprayed fuel can be evaporated and the liquid fuel can be evaporated in the combustion burner 23. For this reason, the energy efficiency of the whole system can be improved.

Thus, in the fuel cell power generation system 100 according to the first embodiment, the air blower 12 is provided by providing the air heating heat exchanger 13 on the output side of the air blower 12 and further providing the combustion burner 23 on the downstream side. The air (oxidizing gas) output more is heated and supplied to the fuel cell 11. Since the temperature of the fuel cell 11 is adjusted by appropriately adjusting the amount of heat generated by the combustion burner 23 according to the power generation output of the fuel cell, it is possible to flexibly cope with fluctuations in the load connected to the fuel cell 11. The generated power can be adjusted.

Further, the exhaust gas discharged from the reformer heater 16 is introduced into the high temperature side passage of the air heating heat exchanger 13, and the air sent from the air blower 12 is converted into the low temperature side of the air heating heat exchanger 13. Since the temperature is raised through the flow path and then supplied to the combustion burner 23, the heat of the air heating heat exchanger 13 such as soot and incombustible fuel that may be generated in the combustion burner 23 is obtained. If it adheres to an exchange part, it can prevent that the substance which will inhibit heat exchange performance accumulates in air heating heat exchanger 13, and it becomes possible to maintain the performance of air heating heat exchanger 13 for a long period of time. Therefore, it is possible to provide a fuel cell power generation system capable of stably changing the power generation output without causing performance degradation or deterioration of the heat exchange means.

Further, even when the combustion burner 23 is not used, the combustion burner 23 itself serves as a passage for the heated air, so that a substance that inhibits the function of the combustion burner 23 is also accumulated in the combustion burner 23. Can be prevented.

Further, the air heating heat exchanger 13 is supplied with the exhaust gas sent from the reformer heater 16 on the high temperature flow path side and heats the air passing through the low temperature flow path side, so that the heat discharged to the outside is reduced. Energy efficiency can be improved.

Further, a part of the anode off-gas discharged from the anode 11b is circulated to the fuel reformer 15, and the remaining anode off-gas is mixed with the cathode off-gas discharged from the cathode 11a. Therefore, the energy of the anode off-gas and the cathode off-gas can be used as a heat source for heating the fuel reformer 15, and the energy efficiency of the entire system can be improved.

[Description of Second Embodiment]
Next, a second embodiment will be described. FIG. 3 is a block diagram showing the configuration of the fuel cell power generation system 100a according to the second embodiment of the present invention, and FIG. 4 is an explanatory diagram showing the detailed configuration of the combustion burner 23. As shown in FIG.

In the fuel cell power generation system 100a according to the second embodiment, as compared with the fuel cell power generation system 100 shown in FIG. 1 described above, the fuel heater 27 (in the front stage of the combustion burner 23 and the front stage of the fuel reformer 15). The difference is that a fuel heating means is provided. Since the other configuration is the same as that of FIG. 1, the same reference numerals are given and the description of the configuration is omitted.

The fuel heater 27 heats the fuel sent from the first fuel pump 14 and the fuel sent from the second fuel pump 22 by the heat of the air heated by the air heating heat exchanger 13. Specifically, as shown in FIG. 4, a high temperature side flow path 27a and two low temperature side flow paths 27b and 27c are provided, and the high temperature side flow path 27a is directed from the air flow control valve 25 to the pre-stage combustor 23a. Connected to the route.

Also, the first low temperature side flow path 27b is connected to the output port of the second fuel pump 22 to heat the fuel delivered from the second fuel pump 22 and supply it to the combustion burner 23. The second low temperature side flow path 27 c is provided at the output port of the first fuel pump 14, heats the fuel sent from the first fuel pump 14, and supplies it to the fuel reformer 15. Therefore, the fuel (liquid fuel) delivered from the first fuel pump 14 can be evaporated and supplied to the fuel reformer 15 using the heat of the air supplied to the pre-stage combustor 23a, and The fuel (liquid fuel) delivered from the second fuel pump 22 can be evaporated and supplied to the fuel injection valves 26a and 26b.

Therefore, when liquid fuel is used as the fuel, it is not necessary to separately provide a heating device for evaporating the fuel, and the device configuration can be simplified.

That is, in the fuel cell power generation system 100a according to the second embodiment, after the system is started, the temperature of the fuel cell 11 rises and the combustion by the combustion burner 23 is stopped, and the fuel reformer 15 supplies the anode 11b for power generation. When the reformed fuel is supplied, the fuel delivered from the first fuel pump 14 is heated by the fuel heater 27 and merged with the anode off-gas in the fuel gas flow path Ll. Is supplied to the container 15. Therefore, the external energy is used only for the heating of the fuel necessary for the operation of the system at the beginning of the start, and after the system is started, the thermal energy of the gas discharged from the system can be recovered and supplied.

Further, in the fuel cell power generation systems 100 and 100a shown in the first and second embodiments described above, a part of the fuel gas discharged from the anode electrode 11b is fuel-modified through the fuel gas flow path Ll. By having a circulation system that supplies to the mass device 15 and a discharge system that introduces only part of the fuel gas discharged from the anode 11b to the reformer heater 16 via the exhaust gas flow path L2, Since power generation components such as hydrogen and water in the reformed fuel gas can be used effectively, high energy efficiency can be achieved.

Furthermore, because of this high energy efficiency, the gas temperature at the outlet of the reformer heater 16 does not become high, but the temperature of the air sent from the air blower 12 can be raised to a temperature suitable for combustion in the combustion burner 23. It is.

Although the fuel cell power generation system of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. be able to.

This application claims priority based on Japanese Patent Application No. 2012-151044 filed on July 5, 2012, the entire contents of which are incorporated herein by reference.

The present invention can be used to operate a fuel cell without causing performance degradation or deterioration of the air heating heat exchanger.

In the fuel cell power generation system according to the present invention, the combustion burner is arranged on the downstream side of the heat exchanging means, so that the performance of the heat exchanging means and the combustion burner is not deteriorated or deteriorated, and the system is started, stopped or operated. Can be performed with high efficiency.

DESCRIPTION OF SYMBOLS 11 Fuel cell 11a Cathode pole 11b Anode pole 12 Air blower 13 Air heating heat exchanger 14 1st fuel pump 15 Fuel reformer 16 Reformer heater 17 Fuel circulation blower 18 Fuel flow path pressure regulation valve 19 Exhaust flow path pressure Adjustment valve 22 Second fuel pump 23 Combustion burner 23a Pre-stage combustor 23b Post-stage combustor 25 Air flow control valve 26a, 26b Fuel injection valve 27 Fuel heater 27a High-temperature side flow path 27b, 27c Low-temperature side flow path 31 Control unit 100, 100a Fuel cell power generation system Ll Fuel gas flow path L2 Exhaust gas flow path

Claims (5)

In a fuel cell power generation system comprising: a fuel cell in which an oxidizing gas is supplied to a cathode electrode and a reformed fuel is supplied to an anode electrode to generate power; and an oxidizing gas supply means for supplying an oxidizing gas to the cathode electrode.
A heat exchanging means that is provided on the output side of the oxidizing gas supply means and heats the oxidizing gas by passing the oxidizing gas to the low-temperature channel side;
A combustion burner provided on the downstream side of the heat exchanging means, and further heating the oxidizing gas after being heated by the heat exchanging means and supplying it to the cathode electrode;
A fuel cell power generation system comprising: The fuel cell power generation system according to claim 1,
The fuel cell power generation system, wherein the heat exchanging means heats the oxidizing gas by heat of exhaust gas of the fuel cell. A fuel cell power generation system according to claim 1 or 2,
A fuel heating means is provided between the heat exchange means and the combustion burner to heat the fuel supplied to the combustion burner by the heat of the oxidizing gas that has passed through the low temperature flow path side of the heat exchange means. Fuel cell power generation system. The fuel cell power generation system according to any one of claims 1 to 3,
The fuel cell comprises reforming means for reforming the fuel supplied from the fuel supply means and supplying the reformed fuel to the fuel cell. The fuel cell includes a cathode electrode supplied with an oxidizing gas, and a reformer output from the reforming means. Having an anode electrode to which fuel is supplied;
A reforming process in which part of the anode off-gas discharged from the anode electrode is circulated to the reforming means, and the remaining anode off-gas is mixed with the cathode off-gas discharged from the cathode electrode to heat the reforming means. A fuel cell power generation system, characterized in that the fuel cell power supply system supplies the heat to the heater heat exchange means. In a fuel cell power generation system comprising: a fuel cell in which an oxidizing gas is supplied to a cathode electrode and a reformed fuel is supplied to an anode electrode to generate power; and an oxidizing gas supply means for supplying an oxidizing gas to the cathode electrode.
Heating the oxidizing gas output from the oxidizing gas supply means by heat exchange;
A control method for a fuel cell power generation system, wherein the oxidizing gas heated by heat exchange is further heated and supplied to the cathode electrode.

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