JP2009158321A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of reducing energy loss likely to be generated at starting, shortening the time required to make starting, and suppressing or preventing a breakage of fuel cell at starting. <P>SOLUTION: The fuel cell system includes a heating device, the fuel cell, and a chemical heat pump, and is structured so that heat from the heating device is supplied to the anode of fuel cell and the chemical heat pump when the system is in the starting mode and that the heat emitted from the chemical heat pump is supplied to the cathode of the fuel cell, characterized in that the relation of Equation (1)¾Tc-Ta¾<ΔTdl is met owing to a controller, where Ta is the anode temperature of the fuel cell, Tc is the cathode temperature, and ΔTdl is the breakage limit temperature difference of the fuel cell. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly, includes a predetermined control device, reduces energy loss required for startup, shortens time required for startup, and suppresses damage of the fuel cell during startup. The present invention also relates to a fuel cell system that can be prevented.

  Conventionally, as a combination of a fuel cell and a chemical heat pump, it is possible to store the exhaust heat of the fuel cell and store hydrogen at the same time, leveling the hydrogen consumption used in the fuel cell A chemical heat storage hydrogen storage device that can be used is disclosed (see Patent Document 1).

JP 2005-85598 A

  However, Patent Document 1 discloses the use of a chemical heat pump during operation of the fuel cell, but does not disclose any use of the chemical heat pump during startup of the fuel cell.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to reduce energy loss required for startup, shorten the time required for startup, and at the time of startup. An object of the present invention is to provide a fuel cell system capable of suppressing or preventing damage to the fuel cell.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, the present inventors have found that the above object can be achieved by providing a predetermined control device, and the present invention has been completed.

That is, the fuel cell system of the present invention is a fuel cell system comprising a heating device, a fuel cell, and a chemical heat pump, and when the fuel cell system is in the start mode, the anode of the fuel cell and the chemical heat pump The heat generated by the chemical heat pump is supplied to the cathode of the fuel cell, and is calculated from the temperature Ta of the anode of the fuel cell and the temperature Tc of the cathode of the fuel cell. Ta | and fuel cell failure limit temperature difference ΔTdl, the following equation (1)
| Tc−Ta | <ΔTdl (1)
It has the control apparatus which satisfies these relationships.

  According to the present invention, since a predetermined control device is provided, etc., a fuel that can reduce energy loss required for startup, shorten time required for startup, and suppress or prevent damage to the fuel cell at startup. A battery system can be provided.

  Hereinafter, an embodiment of a fuel cell system of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element in each drawing, and the overlapping description is abbreviate | omitted.

FIG. 1 is an explanatory diagram of an embodiment of a fuel cell system when the fuel cell system is in a startup mode.
The “start-up mode” is a mode in which the fuel cell is heated to the power generation start temperature when the fuel cell is shifted from the stopped state to the normal operation state.

First, the configuration of the present embodiment will be described.
As shown in the figure, the fuel cell system of the present embodiment includes a heating device 10, a fuel cell 20, a chemical heat pump 30, a fuel tank 40, a compressor 50, an afterburner 60, and a heat exchanger 70. , And a flow path group including flow paths a to u. Furthermore, it has a predetermined control device.

  The heating device 10 may be the start burner 11, or may include the start burner 11 and the reformer 13, and the reformer 13 may be integrated with the start burner 11. Furthermore, it can also be set as the structure by which the vaporizer which vaporizes liquid fuel was comprised in either of said structures.

  The fuel cell 20 includes an anode 21, a cathode 23, and an electrolyte 25.

Although it does not specifically limit as said fuel cell, For example, the operating temperature of a fuel cell shall be 200 degreeC or more.
Examples of the fuel cell having an operating temperature of 200 ° C. or higher include a solid oxide fuel cell using an oxygen ion conductive oxide electrolyte, a medium temperature fuel cell using a proton conductive oxide electrolyte, and a solid acid fuel cell. Examples thereof include a medium temperature operation fuel cell using an electrolyte and a fuel cell using an ionic liquid as an electrolyte.

Further, as the above-described fuel cell, for example, the operating temperature of the fuel cell may be 400 ° C. or higher.
As a fuel cell having an operating temperature of 400 ° C. or more, for example, a perovskite type oxide such as partially stabilized zirconia, ceria, La—Sr—Ga—Mg, BaCeO ₃ or BaZrO ₃ is used as an electrolyte. However, the present invention is not limited to these. That is, for example, a solid acid such as a phosphate system such as La _x M _1-x PO ₄ (M = Sr, Ba) or a borate system such as La _x M _1-x BO ₃ (M = Sr, Ba). There can also be mentioned a fuel cell in which is used as an electrolyte.

  The chemical heat pump 30 includes a first reactor 31 in which a dehydration endothermic reaction of a metal hydroxide that releases water therein and / or a hydration exothermic reaction of the metal oxide, which is the reverse reaction, The second reactor 33 in which vaporization occurs, the communication pipe 35 communicating these, the first heat exchanger 37 provided in the first reactor 31, the second heat exchanger 39 provided in the second reactor 33 And a first control valve B provided in the communication pipe 35 and capable of controlling the internal pressure of the first reactor 31 and the second reactor 33.

As the chemical heat pump as described above, for example, the following reaction formulas (1) and (2)
M (OH) _x → MO _{x / 2} + x / 2H ₂ O (1)
MO _{x / 2} + x / 2H ₂ O → M (OH) _x (2)
And those having a reaction system that causes a dehydration endothermic reaction and a hydration exothermic reaction as shown in FIG. In the reaction formulas (1) and (2), examples of the metal element M include magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and lanthanum. (La).

In the flow channel group, in the drawing, the flow channel having the flow channel a, the flow channel b, and the flow channel c as constituent elements is a first exhaust supply flow channel, and the flow channel having the flow channel d as a constituent element is a second. The exhaust supply flow path and the flow path having the flow path e as constituent elements are referred to as third exhaust supply flow paths.
Here, in the drawing, a flow path indicated by a broken line indicates that various exhaust gases and air are not conducted to the flow path in the start mode.

  The predetermined control device includes a second control valve A, a third control valve C, a fourth control valve D, and a fifth control valve E, and although not shown, an anode side temperature detector, a cathode side temperature detector A control unit is provided.

Next, the operation of this embodiment will be described.
When the fuel cell system of the present embodiment is in the startup mode, the fuel from the fuel tank is supplied to the startup burner, the air from outside the system is supplied to the startup burner, and this is burned in the startup burner.
Note that whether or not the fuel cell system is in the start-up mode is determined by the cooperation of the anode side temperature detector, the cathode side temperature detector, and the control unit. Specifically, the control unit compares the temperature data input to the control unit from the anode-side temperature detector or the cathode-side temperature detector with the fuel cell power generation start temperature data stored in the control unit itself. If the temperature data to be generated is lower than the power generation start temperature, it is determined that the start mode is set.

Then, stoichiometric or rich atmospheric gas, which is exhaust from the heating device including the start burner, is supplied to the anode through the first exhaust supply channel, and the fuel cell is heated from the anode side.
Further, exhaust from the anode is supplied to the second heat exchanger through the first exhaust supply flow path, or stoichiometric or rich atmospheric gas, which is exhaust from a heating device having an activation burner, is supplied to the second exhaust supply flow. The exhaust gas from the anode is supplied to the second heat exchanger through the passage, or the exhaust gas from the anode is supplied to the second heat exchanger through the first exhaust gas supply channel, and the exhaust gas is supplied from the heating device having the start burner. Atmospheric gas is supplied to the second heat exchange through the second exhaust supply channel to heat the second reactor. A catalyst can be supported on the second heat exchanger for the purpose of purifying the exhaust gas and assisting the heating of the second reactor. Also, a part of the exhaust from the second heat exchanger can be mixed with the new fuel introduction line f of the heating device 10 and introduced.

Further, water is vaporized inside the second reactor, and the vaporized water is supplied to the first reactor through the communication pipe.
Furthermore, a hydration exothermic reaction of the metal oxide is caused inside the first reactor to heat the first heat exchanger.

  Furthermore, air is supplied from the compressor to the first heat exchanger, and high-temperature air is supplied to the cathode through the third exhaust supply passage to heat the fuel cell from the cathode side. The cathode exhaust is supplied to a heat exchanger and is exhausted after heat exchange.

  After heating the fuel cell to the power generation start temperature, fuel is supplied to the anode through the vaporizer and reformer provided in the heating device, while air is supplied from the compressor to the cathode, and the fuel cell is operated for power generation. Transition to normal operation state. For example, when a liquid hydrocarbon fuel such as bioethanol or methanol is used, it may be configured to be supplied to the anode through a vaporizer provided in the heating device.

When heating the fuel cell in this way, when the temperature difference between the anode and cathode of the fuel cell is outside the allowable temperature difference reference data of the fuel cell, the adjustment of the opening degree of the first control valve and One or both of the adjustments of the opening degree of the second control valve are performed.
The permissible temperature difference reference data can be appropriately set according to the failure limit temperature difference, the heating rate during heating, and the time interval for adjusting the control valve. For example, the allowable temperature difference reference data can be set to 30 to 80% of the failure limit temperature difference.

By adjusting the second control valve, the ratio of the exhaust introduced into the anode of the fuel cell in the startup burner exhaust can be controlled, and the temperature of the anode can be adjusted.
Thereby, the temperature of the heat radiation driving heat flow introduced into the second heat exchanger can be controlled. Furthermore, by adjusting the first control valve, the pressure in the first reactor can be adjusted, and furthermore, the air flow having a temperature higher than the temperature of the heat flow introduced into the second heat exchanger is changed to the first heat exchanger. Can be taken out from. Thereby, the temperature of the cathode can be adjusted.

  Excess energy generated during power generation operation or stop operation is stored, and during startup, the anode is heated with sensible heat from the startup burner exhaust, and the low-temperature sensible heat is used as the driving heat source to generate a large amount of heat at a high temperature. Since the cathode is heated by releasing heat, it is possible to start up with a small amount of fuel. Thereby, since the energy loss concerning starting can be reduced, the total efficiency from starting to stopping can be improved.

Moreover, since the temperature difference between the heated gases flowing through the two flow paths can be reduced, the thermal stress applied to the fuel cell at the time of rapid heating start-up can be reduced. Furthermore, since the high-temperature gas can be flowed and heated in both the cathode and anode channels, the startup time can be shortened.
Furthermore, the heat supplied from the heating device is the heat using a stoichiometric or rich atmosphere gas as a medium, and the heat supplied from the chemical heat pump is the heat using a stoichiometric or lean atmosphere gas or air as a medium. In addition, it is possible to suppress or prevent the fuel cell from being damaged due to the deterioration of the anode and the cathode.

FIG. 2 is an explanatory view of an embodiment of the fuel cell system when anode exhaust is used when the fuel cell system is in the heat storage operation mode.
The “heat storage operation mode” refers to a case where the fuel cell is operating at a high output, or a case where the required power generation output is 0 and a stop mode is entered, and the fuel cell anode exhaust, cathode exhaust or In this mode, the heat of combustion exhaust gas obtained by combustion processing of anode exhaust is stored in a chemical heat pump using dehydration endothermic reaction of metal hydroxide.

In the flow path group, in the figure, the flow path having the flow path a, the flow path b, the flow path i, the flow path j, the flow path k, and the flow path 1 as constituent elements is defined as a fourth exhaust supply flow path, a flow path. A channel having the channel m as a component is a fifth exhaust supply channel, a channel having the channel n as a component is a sixth exhaust supply channel, and a channel having the channel q and the channel r as components. A flow path including the seventh exhaust supply flow path, the flow path s, and the flow path t as constituent elements is referred to as an eighth exhaust supply flow path.
Here, in the figure, the flow path indicated by a broken line indicates that various exhaust gases and air are not conducted to the flow path in the heat storage operation mode.

When the fuel cell is stopped, for example, in order to suppress oxidative deterioration of the anode electrode and discharge water generated by the reaction, after the generated current becomes zero, the fuel cell is cooled until the temperature drops below a certain temperature. That is good. As a result, fuel that does not contribute to power generation that flows when stopped can be stored as heat, for example, preventing oxidation deterioration of the fuel electrode without reducing efficiency and deterioration such as water freezing and breaking after stopping Then you can stop.
At this time, the temperature can be lowered while circulating the anode exhaust gas again to the anode inlet of the fuel cell. Thereafter, the gas is completely stopped.
When the gas is completely stopped, since the unused fuel is contained in the gas circulating in the anode flow path, it is burned by an afterburner and exhausted at least finally. The sensible heat of the exhaust can be stored in a chemical heat pump and used as part of the startup energy of the next fuel cell.

When the fuel cell system according to the present embodiment is in the heat storage operation mode, the fuel from the fuel tank is supplied to the reformer, and the reformer reforms the fuel.
Then, the reformed fuel is supplied to the anode through the fourth exhaust supply passage to generate electric power.
Further, the exhaust from the anode is supplied to the afterburner through the fourth exhaust supply passage.
Then, the unused fuel that could not be used in the anode is burned together with the air supplied from the compressor.
Combustion exhaust gas is supplied to the heat exchange flow path of the reformer to heat the reformer, and is also supplied to the first heat exchanger of the chemical heat pump to heat the first reactor.
Distribution of heat for heating the reformer and for heating the first reactor can be performed by a valve D.
During normal operation, exhaust from the anode is returned to the reformer through the sixth exhaust supply flow path and supplied to the anode again, or exhaust from the anode is passed through the fifth exhaust supply flow path to the reformer. When the required output decreases, the amount of heat required by the reformer also decreases, while the fuel already supplied from the reformer to the anode is the amount required when the required output is large. Unused fuel supplied to the afterburner increases and combustion heat is left. In such a case, the amount of exhaust distribution to the chemical heat pump can be increased and heat can be stored in the chemical heat pump.

  Then, dehydration endothermic reaction of the metal hydroxide is caused inside the first reactor, and the vaporized water is supplied to the second reactor through the communication pipe.

  In addition, air is supplied from the compressor to the second heat exchanger, and heat storage is performed in the chemical heat pump by promoting the liquefaction reaction (condensation) of water vapor in the second reactor.

  On the other hand, the temperature of the cathode can be adjusted by supplying air through the seventh exhaust supply passage and the eighth exhaust supply passage. Specifically, the cathode exhaust of the fuel cell is passed through a heat exchanger, exchanged with air newly introduced into the cathode of the fuel cell, and then exhausted.

  An example of the operation method of the fuel cell system of this embodiment will be described in more detail. Note that FIG. 1 and FIG. 2 can be referred to for the configuration.

FIG. 3 is a flowchart illustrating an example of the driving method.
In S1, the process starts with an activation signal and proceeds to S2.
In S2, the cathode temperature Tc and the anode temperature Ta are read, and the process proceeds to S3.
In S3, it is determined whether or not Ta <T2 is satisfied. If satisfied (YES), the process proceeds to S4. That is, the anode temperature Ta is measured, and when it is lower than the set temperature T2, the mode is switched to the start mode. Here, T2 is a power generation start temperature.
In S4, an activation mode routine is performed, and the process proceeds to S2.
On the other hand, in S3, it is determined whether Ta <T2 is satisfied. If not satisfied (NO), the process proceeds to S5.
In S5, power is generated in the power generation mode, and the process proceeds to S6.
In S6, it is determined whether or not the required power generation output is 0, and if it is satisfied (YES), the process proceeds to S7. That is, the anode temperature Ta is measured, and when the required power generation output becomes 0 when the temperature is equal to or higher than the set temperature T2, the mode is switched to the heat storage mode.
In S7, a heat storage operation mode routine is performed, and the process proceeds to S8.
In S8, it is stopped by a stop signal.

FIG. 4 is a flowchart illustrating an example of a startup mode routine in an example of an operation method.
In S4a, start mode valve opening / closing control is performed, air is introduced into the first heat exchanger (V1), anode exhaust and exhaust gas burned with fuel in the start burner are introduced into the second heat exchanger (V2), and the process proceeds to S4b.
In S4b, ΔT = Ta−Tc is calculated, allowable temperature difference reference data T1 which is a value set from the failure limit temperature difference ΔTdl or the like is read, and the process proceeds to S4c.
In S4c, it is determined whether or not ΔT> T1 is satisfied. If satisfied (YES), the process proceeds to S4d.
In S4d, one or both of the valve opening settings of increasing the pressure of the first control valve (hereinafter abbreviated as “valve A”) and increasing the bypass introduction amount of the valve B are performed, and S4e Proceed to
In S4e, the valve A and valve B open / close control signals are output and the process returns.
On the other hand, it is determined whether or not ΔT> T1 is satisfied in S4c. If not satisfied (NO), the process proceeds to S4f.
In S4f, one or both of the valve opening settings for decreasing the pressure of the valve A and increasing the anode introduction amount of the valve B are set, and the process proceeds to S4e.

In the start-up mode, the cathode temperature Tc is measured, and the difference ΔT between Ta and Tc is detected. If this is larger than the set value T1, the pressure in the first reactor is increased by the valve B, and the anode is The exhaust gas temperature introduced into the first heat exchanger of the first reactor is increased by adjusting the introduction ratio into the first reactor. As a result, the temperature of the air discharged from the second heat exchanger and introduced into the cathode is increased.
On the other hand, when ΔT is smaller than the set value T1, the valves B and A are adjusted to increase the exhaust amount entering the anode. The anode temperature and the cathode temperature can also be measured as gas temperatures immediately after the anode and cathode are discharged, and can also be measured as the contact temperature in the electrode in the anode or the cathode or in the vicinity of the electrode. Thereby, in the fuel cell system, the temperature difference between the anode and the cathode can be reduced and heated, so that the fuel cell system is highly reliable and is prevented from being damaged by the heating accompanying the start-up.

FIG. 5 is a flowchart illustrating an example of a heat storage operation mode routine in an example of the operation method.
In S7a, the operation mode valve opening / closing control is performed, the exhaust gas burned with unused fuel in the afterburner is introduced into the first heat exchanger (V1), the air is introduced into the second heat exchanger (V2), and the process proceeds to S5b. .
In S7b, a required power value is set, and the process proceeds to S5c.
In S7c, the introduction fuel flow rate and the valve C circulation rate are set, and the process proceeds to S7d.
In S7d, the reformer temperature Tr is read, and the process proceeds to S7e.
In S7e, it is determined whether or not Tr <T3 is satisfied. If satisfied (YES), the process proceeds to S7f. Here, T3 is the target reformer temperature.
In S7f, the distribution to the reforming of the valve D is set to be increased, and the process proceeds to S7g.
In S7g, the valve D distribution control signal is output and the process returns.
On the other hand, in S7e, it is determined whether or not Tr <T3 is satisfied. If not satisfied (NO), the process proceeds to S7h.
In S7h, the distribution to the first heat exchanger (V1) of the chemical heat pump (CHP) of the valve D is set to be increased, and the process proceeds to S7g.

  For example, when starting up in a short time after stopping the fuel cell last time, the temperature of the fuel cell has not decreased so much, so there is no need to use the heat stored in the chemical heat pump for startup, When it is not necessary to start up and only a heat supply is required, the heat stored in the chemical heat pump can be used for preheating of devices other than the fuel cell such as air conditioner, hot water supply, battery and engine.

It is one Embodiment of a fuel cell system, Comprising: It is explanatory drawing when the said fuel cell system is a starting mode. FIG. 3 is an explanatory view when an anode exhaust is used in an embodiment of a fuel cell system when the fuel cell system is in a heat storage operation mode. It is a flowchart which shows an example of the driving | running method. It is a flowchart which shows an example of the starting mode routine in an example of an operation method. It is a flowchart which shows an example of the thermal storage operation mode routine in an example of an operation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heating apparatus 11 Startup burner 13 Reformer 20 Fuel cell 21 Anode 23 Cathode 25 Electrolyte 30 Chemical heat pump 31 First reactor 33 Second reactor 35 Communication pipe 37 First heat exchanger 39 Second heat exchanger 40 Fuel tank 50 Compressor 60 Afterburner 70 Heat exchanger A, B, C, D, E First to fifth control valves a to u flow paths

Claims (2)

A fuel cell system comprising a heating device, a fuel cell, and a chemical heat pump,
When the fuel cell system is in start-up mode, heat from the heating device is supplied to the anode of the fuel cell and the chemical heat pump, and heat generated by the chemical heat pump is supplied to the cathode of the fuel cell. And | Tc−Ta | calculated from the temperature Ta of the anode of the fuel cell and the temperature Tc of the cathode of the fuel cell and the failure limit temperature difference ΔTdl of the fuel cell, the following equation (1)
| Tc−Ta | <ΔTdl (1)
Having a control device that satisfies the relationship
A fuel cell system.   The heat supplied from the heating device is heat using a stoichiometric or rich atmosphere gas as a medium, and the heat supplied from the chemical heat pump is heat using a stoichiometric or lean atmosphere gas or air as a medium. The fuel cell system according to claim 1.

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