JP2006019081A - Solid oxide fuel cell system and driving method of solid oxide fuel cell system - Google Patents

Abstract

To achieve uniform temperature distribution of a solid oxide fuel cell system without increasing the air flow rate, and to destroy or activate an overvoltage of the solid oxide fuel cell due to thermal stress caused by excessive temperature distribution. Solve various problems such as increased electrical resistance.
A plurality of solid oxide fuel cells 11 that generate power through a reaction between hydrogen gas and air are arranged in an air flow direction FA. Next, a plurality of reformers 12 for reforming the hydrocarbon fuel gas into the hydrogen gas and carbon monoxide gas are arranged in the air flow direction FA. Thus, the temperature rise of the air between the solid oxide fuel cells 11 is suppressed, and the temperature distribution in the solid oxide fuel cell system 10 including the solid oxide fuel cell 11 and the reformer 12 is made uniform. To embody.
[Selection] Figure 1

Description

  The present invention relates to a solid oxide fuel cell system and a driving method of the solid oxide fuel cell system.

  Since the solid oxide fuel cell operates at a high temperature of about 1000 ° C., it is possible to recover power from a high-temperature exhaust heat generated simultaneously with power generation using a heat engine or the like. In addition, since the exhaust heat can be used for the steam reforming reaction of hydrocarbon fuel gas, which is an endothermic reaction, an extremely efficient system can be constructed.

  A solid oxide fuel cell stack is a battery part in which a solid electrolyte that permeates oxygen ions is sandwiched between an air side electrode and a fuel side electrode, a flow path part through which fuel and air flow on both sides, and a current collector that collects generated electricity And a manifold section for supplying and discharging fuel, air and exhaust gas to and from the flow path. Usually, a solid oxide fuel cell system is configured including a reformer for reforming hydrocarbon fuel, a fuel air supply unit, and the like.

  Since a solid oxide fuel cell operates at a high temperature, a ceramic material is generally used. For this reason, if excessive temperature distribution occurs in the battery, problems such as the occurrence of destruction due to thermal stress, increase in activation overvoltage and electrical resistance, and the like occur. Normally, the temperature distribution is made uniform by increasing the flow rate of air that also serves as cooling together with the oxidizing agent.

  However, since the basic member of the solid oxide fuel cell is ceramic, reliability problems such as destruction due to thermal stress and reaction between materials at a hot spot occur when an excessive temperature distribution occurs. In addition, in the low temperature part, the activation overvoltage at the electrode increases, and the ionic conductivity of the electrolyte decreases, which causes the efficiency of the solid oxide fuel cell to decrease. In addition, there is a problem that the current density is distributed at the same time as the temperature distribution, and excessive ohmic loss occurs in a region where the theoretical electromotive force is large.

  Also, if the air flow rate is increased to make the temperature distribution uniform, extra air blowing power is required to increase the air flow rate, and the exhaust system temperature decreases, so the efficiency of the entire system decreases. Therefore, there is a problem that auxiliary equipment and piping are large and expensive.

  The present invention aims to make the temperature distribution of a solid oxide fuel cell system uniform without increasing the air flow rate, and destroy or activate overvoltage of the solid oxide fuel cell due to thermal stress caused by excessive temperature distribution. And it aims at solving various problems, such as an increase in electrical resistance.

In order to achieve the above object, the present invention provides:
A plurality of reformers for reforming hydrocarbon fuel gas into hydrogen gas and carbon monoxide gas;
Comprising a plurality of solid oxide fuel cells that generate electricity through a reaction between the hydrogen gas and air,
The plurality of reformers and the plurality of solid oxide fuel cells are arranged in the air flow direction, and relate to a solid oxide fuel cell system.

The present invention also provides:
Disposing a plurality of solid oxide fuel cells that generate power through a reaction between hydrogen gas and air in the air flow direction;
Arranging a plurality of reformers for reforming hydrocarbon fuel gas into the hydrogen gas and carbon monoxide gas in the flow direction of the air,
The temperature rise of the air between the solid oxide fuel cells is suppressed, and the temperature distribution in the solid oxide fuel cell system including the solid oxide fuel cells and the reformer is made uniform. The present invention relates to a method for driving a solid oxide fuel cell system.

  According to the present invention, a solid oxide fuel cell system is configured from a plurality of solid oxide fuel cells instead of a single solid oxide fuel cell, and the plurality of solid oxide fuel cells are used for power generation. It arranges in the flow direction of the supplied air. Each solid oxide fuel cell is sufficiently small compared to a conventional single solid oxide fuel cell, so that the heat conduction inside the object is more dominant than the heat conduction from the object surface. Thus, the biot number, which is the ratio between the so-called internal thermal resistance and convective thermal resistance, becomes small. As a result, by arranging the plurality of solid oxide fuel cells to form a solid oxide fuel cell system, the temperature rise width between the solid oxide fuel cells is reduced, and the solid oxide fuel cell system is reduced. The temperature distribution of the fuel cell system can be made uniform.

  Therefore, the temperature distribution of the solid oxide fuel cell system is made uniform without increasing the air flow rate, and the solid oxide fuel cell is destroyed or activated overvoltage and electrical due to thermal stress caused by excessive temperature distribution. Various problems such as an increase in resistance can be solved.

  The reformer is provided for reforming hydrocarbon fuel gas into hydrogen gas and carbon monoxide gas and supplying the reformed gas to the solid oxide fuel cell.

  The reformer undergoes a steam reforming reaction, which is an endothermic reaction, at the inlet. Accordingly, by arranging the reformer and the solid oxide fuel cell alternately and uniformly, the heat generated by the solid oxide fuel cell can be offset by the endotherm generated by the reformer. . As a result, the solid oxide fuel cell system can have an isothermal portion including the reformer and the solid oxide fuel cell.

  On the other hand, air used for power generation also functions as a cooling gas. Therefore, when the air is directly introduced into the isothermal part, the isothermal part cannot maintain the temperature uniformly by cooling with the air. Therefore, a temperature raising part is provided in front of the isothermal part, that is, at the entrance side of the solid oxide fuel cell system, so that the air is sufficiently heated to eliminate the influence on the isothermal part. Since the solid oxide fuel cell generates heat accompanying power generation, the temperature raising unit can be constituted by the solid oxide fuel cell, for example. However, the temperature raising unit can be configured by other methods.

  In particular, in the isothermal part, in order to promote the uniformization of the temperature distribution, the solid oxide fuel cell and the reformer are preferably arranged alternately in the air flow direction. .

  Further, the length of the reformer can be made substantially equal to the length of the steam reforming reaction region generated at the inlet of the reformer. In this case, since the entire reformer is subjected to the endothermic action of the steam reforming reaction and is sufficiently cooled, the heat generation of the solid oxide fuel cell in the isothermal portion is particularly sufficient. It cancels out and the temperature distribution can be kept more uniform. However, in the actual solid oxide fuel cell system, the length of the reformer is determined in consideration of the overall design design.

  Note that “substantially equal” means that the length of the reformer and the length of the steam reforming reaction region are substantially equal within an allowable range in which the above-described effects can be obtained. For example, when the length of the reformer is L1 and the length of the steam reforming reaction region is L2, the relationship of 80% ≦ L1 / L2 ≦ 120% is satisfied.

  Furthermore, the reformer and the solid oxide fuel cell can be arranged so as to be substantially perpendicular to each other. In this case, the reformer and the solid oxide fuel cell can be arranged in any number in the vertical direction of each other. The temperature distribution of the entire fuel cell system can be made uniform, and for example, the isothermal portion can be easily realized.

  As described above, according to the present invention, the temperature distribution of the solid oxide fuel cell system is made uniform without increasing the air flow rate, and the solid oxide form due to thermal stress caused by excessive temperature distribution is achieved. Various problems such as destruction of the fuel cell, activation overvoltage and increase in electric resistance can be solved.

  The details of the present invention and other features and advantages will be described in detail below based on the best mode.

  FIG. 1 is a block diagram showing a preferred example of a solid oxide fuel cell system of the present invention. A solid oxide fuel cell system 10 shown in FIG. 1 includes a plurality of tubular solid oxide fuel cells 11 and a plurality of tubular reformers 12. Each of the solid oxide fuel cells 11 stands upright and is arranged in the air flow direction FA, and each of the reformers 12 is substantially perpendicular to the solid oxide fuel cell 11 at regular intervals. In a state of being stacked in the vertical direction, they are arranged behind the air flow direction FA.

  A hydrocarbon fuel gas is introduced into the reformer 12 along with, for example, water vapor from the direction indicated by the arrow FC, and reformed into hydrogen gas and carbon monoxide gas. The resulting reformed gas (hydrogen gas and carbon monoxide gas) exits the reformer 12 and is then introduced into the solid oxide fuel cell 11 as indicated by an arrow FM. The solid oxide fuel cell 11 includes a solid electrolyte 111 that transmits oxygen ions and hydrogen ions, and an electrode portion 112 that is provided so as to sandwich the solid electrolyte 111.

  Therefore, in the solid oxide fuel cell 11, power generation occurs through a chemical reaction between the hydrogen gas and the carbon monoxide gas introduced into the interior and oxygen in the air flowing through the outer peripheral portion thereof. Therefore, the solid oxide fuel cell system 10 shown in FIG. 1 can be put to practical use as a battery system by taking out the electricity generated by the power generation from a pyroelectric unit (not shown).

  In the power generation reaction described above, not all of the reactions by the air and the hydrogen gas contribute to power generation, but also contribute to heat generation at a considerable rate. However, since the solid oxide fuel cell 11 shown in FIG. 1 is sufficiently downsized compared to a conventional single oxide fuel cell, the heat conduction inside the object is caused by heat from the object surface. It becomes more dominant than conduction, and the biot number, which is the ratio of so-called internal thermal resistance and convective thermal resistance, becomes small. As a result, the temperature rise width between the solid oxide fuel cells 11 is reduced, and the temperature distribution of the solid oxide fuel cell system 10 can be made uniform.

  Therefore, the temperature distribution of the solid oxide fuel cell system is made uniform without increasing the air flow rate, and the conventional solid oxide fuel cell is destroyed or activated by thermal stress caused by excessive temperature distribution. Various problems such as overvoltage and increase in electrical resistance can be solved.

  In the solid oxide fuel cell system 10 shown in FIG. 1, the size of each solid oxide fuel cell 11 can be 50 mm or less in diameter in the case of a cylindrical shape, The diameter of the flat portion can be 1 mm to 50 mm. In any case, the length can be 50 mm or more.

  In the solid oxide fuel cell system 10 shown in FIG. 1, only the solid oxide fuel cells 11 are arranged on the upstream side of the air flow direction FA, that is, on the inlet side of the air. As described above, since heat is generated from the solid oxide fuel cell 11 together with power generation, this region constitutes the temperature raising unit 20 that raises the temperature of the air.

  On the other hand, on the downstream side of the air flow direction FA, that is, on the air outlet side, the solid oxide fuel cells 11 and the reformers 12 are alternately arranged at substantially right angles. In the reformer 12, a steam reforming reaction that is an endothermic reaction occurs at the inlet portion thereof, and in this region, the heat generation in the solid oxide fuel cell 11 and the heat absorption in the reformer 12 are balanced to cancel each other. You can make them meet each other. Accordingly, the temperature does not change in the region, and the isothermal part 30 is configured.

  Since the solid oxide fuel cell system 10 shown in FIG. 1 has the isothermal portion 30, the temperature distribution of the entire system can be made extremely uniform.

  Since the air used for power generation also functions as a cooling gas, when the air is directly introduced into the isothermal part 30, the isothermal part 30 cannot maintain the temperature uniformly by cooling with the air. . Therefore, by providing the heating unit 20 in front of the isothermal unit 30, that is, at the entrance side of the solid oxide fuel cell system 10, the temperature of the air is sufficiently increased before being introduced into the isothermal unit 30. Therefore, excessive cooling that disturbs the isothermal property of the isothermal part 30 does not occur. As a result, the temperature distribution of the entire system can be made extremely uniform.

  Further, in the solid oxide fuel cell system 10 shown in FIG. 1, the solid oxide fuel cells 11 and the reformers 12 are alternately arranged in the isothermal section 30. Heat generation by the solid oxide fuel cell 11 and heat absorption by the reformer 12 can be effectively offset, and the temperature distribution in the isothermal section 30 can be made more uniform.

  Further, in the solid oxide fuel cell system 10 shown in FIG. 1, the reformer 12 is arranged so as to be substantially perpendicular to the solid oxide fuel cell 11, so that the reformer 12 and the solid oxide are disposed. The fuel cells 11 can be arranged in an arbitrary number in the vertical direction. Therefore, by appropriately controlling the number thereof, the temperature distribution of the entire solid oxide fuel cell system can be made uniform, and for example, the isothermal section 30 can be easily realized.

  Further, the length of the reformer 12 can be made substantially equal to the length of the steam reforming reaction region generated at the inlet portion of the reformer 12. In this case, since the entire reformer 12 is subjected to the endothermic action of the steam reforming reaction and is sufficiently cooled, in particular, the heat generated by the solid oxide fuel cell 11 in the isothermal portion 30 is sufficiently increased. It cancels out and the temperature distribution can be kept more uniform. Note that “substantially equal” is as defined in paragraph [0017].

  FIG. 2 is a schematic configuration diagram of an actual cell stack of the solid oxide fuel cell system shown in FIG. The battery stack 40 shown in FIG. 2 is configured by stacking a plurality of manifold plates 15. A solid oxide fuel cell 11 is incorporated in the upper manifold plate 15 to constitute the above-described temperature raising unit 20. In the lower manifold plate 15, the solid oxide fuel cell 11 and the reformer 12 are alternately incorporated to constitute the isothermal portion 30 described above.

  In both the temperature raising unit 20 and the isothermal unit 30, the manifold plate 15 is provided between the solid oxide fuel cells 11 provided on the adjacent manifold plates 15 or between the solid oxide fuel cells 11 and the reformer 12. It is connected by the opening provided in.

  For example, in the isothermal part 30, one manifold plate 15 is provided with openings 15A to 15C, and the manifold plate 15 adjacent thereto is provided with openings 15D to 15F. As indicated by the arrow FC, the hydrocarbon fuel gas is introduced into the reformer 12 through the opening 15A, and the obtained reformed gas is discharged toward the opening 15B. The reformed gas is introduced into the solid oxide fuel cell 11 through an opening 15D connected to the opening 15B and an opening 15E connected to the opening 15B provided in the lower manifold plate 15.

  Note that air to be used for power generation is supplied through a through-hole formed by connecting openings 15C and 15F of the manifold plate 15 through the battery stack 40, for example, as indicated by an arrow FA.

  Electricity generated by the power generation reaction of the solid oxide fuel cell 11 is taken out through pyroelectric portions 16 provided at both ends in the length direction of the solid oxide fuel cell 11.

  As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes are made without departing from the scope of the present invention. It can be changed.

It is a block diagram which shows a preferable example of the solid oxide fuel cell system of this invention. It is a schematic block diagram of the actual battery stack of the solid oxide fuel cell system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solid oxide fuel cell system 11 Solid oxide fuel cell 12 Reformer 15 Manifold plate 16 Pyroelectric part 20 Temperature rising part 30 Isothermal part FA Air flow direction FC Hydrocarbon fuel gas flow direction FM Reformed gas Flow direction of hydrogen gas and carbon monoxide gas

Claims (18)

A plurality of reformers for reforming hydrocarbon fuel gas into hydrogen gas and carbon monoxide gas;
Comprising a plurality of solid oxide fuel cells that generate electricity through a reaction between the hydrogen gas and air,
The solid oxide fuel cell system, wherein the plurality of reformers and the plurality of solid oxide fuel cells are arranged in a flow direction of the air.   2. The solid oxide fuel cell system according to claim 1, further comprising an isothermal portion including the solid oxide fuel cell and the reformer.   3. The solid oxide fuel cell system according to claim 2, further comprising a temperature raising unit configured of the solid oxide fuel cell on the air inlet side. 4.   4. The solid according to claim 1, wherein the solid oxide fuel cell and the reformer are alternately arranged in the air flow direction in the isothermal portion. Oxide fuel cell system.   5. The solid according to claim 1, wherein a length of the reformer is substantially equal to a length of a steam reforming reaction region generated at an inlet of the reformer. Oxide fuel cell system.   The solid oxide fuel cell system according to any one of claims 1 to 5, wherein the reformer and the solid oxide fuel cell are arranged so as to be substantially perpendicular to each other.   The reformer is a tubular reformer, and the hydrocarbon fuel gas is converted into the hydrogen gas and the carbon monoxide gas by flowing the hydrocarbon fuel gas through the reformer. The solid oxide fuel cell system according to any one of claims 1 to 6, wherein the solid oxide fuel cell system is configured.   The solid oxide fuel cell is a tubular solid oxide fuel cell, wherein the hydrogen gas and the carbon monoxide gas flow in the solid oxide fuel cell, and the air is the solid oxide fuel cell. 8. The power generation of the solid oxide fuel cell by flowing through the outer periphery of the battery through a reaction between the hydrogen gas, the carbon monoxide gas, and the air. The solid oxide fuel cell system according to any one of the above.   The plurality of reformers and the plurality of solid oxide fuel cells are respectively fixed to a manifold plate and connected to each other through an opening formed in the manifold plate. The solid oxide fuel cell system according to any one of the above. Disposing a plurality of solid oxide fuel cells that generate power through a reaction between hydrogen gas and air in the air flow direction; and
Arranging a plurality of reformers for reforming hydrocarbon fuel gas into the hydrogen gas and carbon monoxide gas in the flow direction of the air,
The temperature rise of the air between the solid oxide fuel cells is suppressed, and the temperature distribution in the solid oxide fuel cell system including the solid oxide fuel cells and the reformer is made uniform. A method for driving a solid oxide fuel cell system.   The isothermal part composed of the solid oxide fuel cell and the reformer due to the uniform temperature distribution of the solid oxide fuel cell system is formed. The method for driving a solid oxide fuel cell system according to claim 10.   12. The solid oxide fuel cell system according to claim 11, wherein a temperature raising portion constituted by the solid oxide fuel cell is formed on an inlet side of the air. 13.   13. The solid oxidation according to claim 10, wherein in the isothermal portion, the solid oxide fuel cell and the reformer are alternately arranged in the air flow direction. Driving method for physical fuel cell system.   14. The solid according to claim 10, wherein a length of the reformer is substantially equal to a length of a steam reforming reaction region generated at an inlet of the reformer. Driving method of oxide fuel cell system.   The solid oxide fuel cell system according to any one of claims 10 to 14, wherein the reformer and the solid oxide fuel cell are disposed so as to be substantially perpendicular to each other. Driving method.   The reformer is a tubular reformer, and the hydrocarbon fuel gas is converted into the hydrogen gas and the carbon monoxide gas by flowing the hydrocarbon fuel gas through the reformer. The driving method of the solid oxide fuel cell system according to any one of claims 10 to 15, wherein the driving method is configured.   The solid oxide fuel cell is a tubular solid oxide fuel cell, wherein the hydrogen gas and the carbon monoxide gas flow in the solid oxide fuel cell, and the air is the solid oxide fuel cell. The fuel cell according to any one of claims 10 to 16, wherein in the solid oxide fuel cell, electric power is generated through a reaction between the hydrogen gas, the carbon monoxide gas, and the air by flowing in the outer periphery of the battery. The driving method of the solid oxide fuel cell system according to any one of the above.   The plurality of reformers and the plurality of solid oxide fuel cells are fixed to a manifold plate and connected to each other through an opening formed in the manifold plate. The driving method of the solid oxide fuel cell system according to any one of the above.

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