JP5007045B2 - Indirect internal reforming type solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to an indirect internal reforming solid oxide fuel cell having a reformer in the vicinity of the fuel cell.

  In a solid oxide fuel cell (hereinafter sometimes referred to as SOFC), a reforming raw material such as kerosene is reformed into a reformed gas containing hydrogen, and the reformed gas is used as fuel for the SOFC. Supply is done. As the reforming reaction, a steam reforming reaction with endotherm is mainly used.

Since the operating temperature of the SOFC is high and close to the reforming temperature of the reforming raw material fuel, there is an indirect internal reforming SOFC in which a reformer is arranged at a position where it receives heat radiation from the SOFC and the heat of the SOFC is used for reforming. Yes (see Patent Document 1).
JP 2002-358997 A

  However, when high-order hydrocarbons such as kerosene are used as the reforming raw material, if hydrocarbon components that have not undergone reforming are supplied to a solid oxide fuel cell having a high operating temperature, the stability of operation due to carbon deposition. May be damaged. Therefore, it is desired to completely convert higher-order hydrocarbons such as kerosene to C1 compounds (compounds having 1 carbon atom).

  During steady operation that can sufficiently receive fuel cell exhaust heat, a high conversion rate can be maintained if a sufficient heat receiving area is given to the reformer by system design, but the amount of fuel cell exhaust heat is reduced due to load fluctuations and disturbances. When the amount is reduced or when the amount of reforming raw material is rapidly increased, the amount of heat necessary for reforming may be insufficient, which may cause a reduction in conversion rate during reforming. At this time, it is conceivable to reduce the conversion rate by reducing the fuel utilization rate of the fuel cell to increase the amount of heat of the anode offgas and heating the reformer with the combustion heat of the anode offgas. In this case, since the reformed fuel is burned and supplied with heat, the efficiency is greatly reduced.

  Further, when the entire reformer receives radiant heat transfer from the solid oxide fuel cell, when the solid oxide fuel cell reaches a steady state, it is heated almost evenly to the vicinity of the reforming raw material inlet of the reformer, Since the temperature is high, carbon may be deposited on the catalyst in the vicinity of the reforming raw material inlet, resulting in abnormal deterioration of the catalyst.

  An object of the present invention is to provide an indirect internal reforming solid oxide fuel cell that uses kerosene as a reforming raw material, and can be stably operated without abnormally degrading the reforming catalyst or reducing the efficiency. An indirect internal reforming solid oxide fuel cell is provided.

According to the present invention, a reformer capable of reforming kerosene, a solid oxide fuel cell using the reformed gas obtained from the reformer as a fuel, and a burner for heating the reformer are provided. And
The reformer is disposed between the solid oxide fuel cell and the burner;
The reformer has a first reforming section and a second reforming section communicating with each other;
Regarding the flow of the reformed gas, the first reforming section is located upstream and the second reforming section is located downstream,
The second reforming section is disposed at a position that receives heat radiation from the solid oxide fuel cell and blocks heat radiation from the solid oxide fuel cell to the first reforming section. Indirect internal reforming type solid oxide fuel cell ,
Further, it has a reforming material preheater directly connected to the reformer inlet for vaporizing, preheating and mixing kerosene and water.
An indirect internal reforming solid oxide fuel cell is provided.

The reforming catalyst filled in the first reforming unit and the second reforming unit may include a reforming catalyst having kerosene oxidation activity.
The burner may be a burner that burns kerosene, and in particular, may be a surface combustion burner that burns kerosene and is disposed with the combustion surface facing downward.

  According to the present invention, an indirect internal reforming solid oxide fuel cell using kerosene as a reforming raw material can be operated stably without abnormally degrading the reforming catalyst or reducing the efficiency. A reformed solid oxide fuel cell is provided.

  In the reformer, a reformed gas that is a gas containing hydrogen is produced from kerosene that is a reforming raw material by a steam reforming reaction. Although partial oxidation reforming reaction may be accompanied at this time, steam reforming is made dominant from the viewpoint of efficiently producing hydrogen. Therefore, in the reformer, the reaction that becomes endothermic by the overall proceeds.

  The reformer has a first reforming section and a second reforming section that communicate with each other. With respect to the flow of the reformed gas, the first reforming section is located on the upstream side and the second reforming section is located on the downstream side. That is, the reforming raw material is supplied to the first reforming section, and the gas exiting the first reforming section flows into the second reforming section.

  Both the first reforming section and the second reforming section are filled with a reforming catalyst capable of reforming kerosene. As the reforming catalyst, a steam reforming catalyst or an autothermal reforming catalyst (a catalyst having steam reforming ability and partial oxidation reforming ability) can be used. The kerosene used can be appropriately selected from known catalysts capable of steam reforming or autothermal reforming.

  It is preferable that the reforming catalyst filled in the first reforming section and the second reforming section includes a reforming catalyst having kerosene oxidation activity. Kerosene oxidation activity refers to the ability to generate heat by oxidizing kerosene with oxygen on the catalyst. By charging the reforming section with a catalyst having oxidation activity, heat is directly generated on the catalyst, and the time until the reforming catalyst reaches a temperature suitable for reforming can be shortened.

  The indirect internal reforming SOFC of the present invention has a burner for heating the reformer in addition to the reformer and the SOFC. The burner can be appropriately selected from known burners capable of burning the burner fuel to be used.

  As the burner fuel, it is preferable to use kerosene used as a reforming raw material. This is because it is not necessary to prepare a separate fuel. However, other fuels can be used.

  As the SOFC, various shapes such as a flat plate type and a cylindrical type can be appropriately selected and employed. The SOFC may be a single cell, but in practice, a stack in which a plurality of single cells are arranged is preferably used. In this case, one or more stacks may be used. The SOFC, the reformer, and the burner can be accommodated in a container such as a can and modularized.

  The reformer is disposed between the SOFC and the burner. That is, both the first reforming unit and the second reforming unit are disposed between the SOFC and the burner.

  The second reforming section is arranged at a position where direct radiation heat transfer from the SOFC to the second reforming section is possible. The direct radiant heat transfer from the SOFC to the first reforming section is blocked by the second reforming section.

  In the indirect internal reforming SOFC of the present invention, even if the heat supply is insufficient with only the exhaust heat of the fuel cell due to disturbance or a rapid increase in the reforming amount, the shortage of heat can be compensated by the combustion heat of the burner. Stable operation is possible without lowering. When the heat necessary for reforming can be provided only by SOFC exhaust heat, burner combustion may not be performed.

  Furthermore, since the second reforming section can receive the radiant heat from the SOFC, the first reforming section blocks the radiant heat from the SOFC by the second reforming section. Compared to the second reforming part, it is easy to lower the temperature. Accordingly, the inlet side of the reformer can be made lower in temperature, thereby making it easier to suppress carbon deposition.

  Furthermore, the reforming raw material preheater can be directly connected to the reformer inlet. The reforming raw material preheater refers to a heat exchanger that vaporizes, preheats and mixes raw materials for obtaining reformed gas containing hydrogen, that is, kerosene and water. By directly connecting the preheater to the first reforming section, the preheater can be efficiently warmed by heat transfer from the reforming section. In addition, it becomes easy to lower the reforming unit inlet to a temperature at which the reforming catalyst does not deteriorate abnormally by heat transfer from the reforming unit to the preheater.

  The temperature of the preheater is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and further preferably 250 ° C. or higher so that kerosene can be vaporized stably. In order to prevent carbon deposition in the preheater, the temperature is preferably 500 ° C. or less, more preferably 450 ° C. or less, and still more preferably 400 ° C. or less.

  The inlet temperature of the first reforming section is preferably 300 ° C. or higher, more preferably 350 ° C. or higher, more preferably 400 ° C. or higher, in order to prevent recondensation of the gasified raw material and to effectively operate the catalyst. And Further, in order to prevent carbon deposition at the catalyst inlet, it is preferably 550 ° C. or lower, more preferably 500 ° C. or lower, and further preferably 450 ° C. or lower.

  In order to efficiently transfer heat between the reforming raw material preheater and the first reforming section, a structure integrated with an outer plate is desirable.

[Example 1]
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited by this. FIG. 1 is a schematic diagram showing an internal reforming SOFC of the present embodiment.

  The indirect internal reforming SOFC of the present embodiment includes a burner 1, a reformer 2, and a SOFC stack 4 in which a plurality of cylindrical SOFCs 3 are arranged in a container (not shown).

  Air and kerosene can be supplied to the burner 1 for combustion, and kerosene is burned here. The burner is preferably a surface combustion burner having a high ratio of radiant heat and a large combustion surface. As the surface combustion burner, for example, a burner using a ceramic plate or a metal mat on the combustion surface can be used.

  Kerosene and water are supplied to the reforming raw material preheater 5, both of which are vaporized and mixed sufficiently.

  The reformer 2 is supplied with kerosene and water vaporized by the reforming raw material preheater to perform steam reforming.

  The reformer stacks two rectangular parallelepiped boxes for forming a gas flow path, and provides a gas supply port at the end of the flow path of the first box (on the right side in FIG. 1), opposite to the gas supply port. Two boxes communicate with each other at the channel end (left side in FIG. 1), and the channel end opposite to the communication end of the second box (that is, the gas supply port of the first box is provided). The same end as the end on the right side (the right side of the drawing in FIG. 1) is provided with a gas outlet, and the first box and the second box are filled with a steam reforming catalyst capable of reforming kerosene. Have. The portion of the first box filled with the reforming catalyst is the first reforming portion 2a, and the portion of the second box filled with the reforming catalyst is the second reforming portion 2b. That is, the reformer has a structure in which the internal gas flow is turned back.

  In addition to the box shape, for example, it is also possible to form a reformer having first and second reforming portions by arranging circular tubes in a planar shape with substantially no gap and turning them back.

  The reformer is arranged between the SOFC and the burner with the first reforming section on the burner side and the second reforming section on the SOFC side. The exhaust heat of SOFC can be received by radiation from the wall surface of the second reforming section, and the combustion heat of the burner can be received from the wall surface of the first reforming section.

  Kerosene is reformed by a reformer to form a reformed gas containing hydrogen and supplied to the anode electrode 3a of the SOFC. On the other hand, an oxygen-containing gas (here, air) is supplied to the cathode electrode 3c. The SOFC generates heat with power generation, and the heat is radiated from the SOFC to the second reforming section. Thus, the SOFC exhaust heat is utilized for the endothermic reaction of the reforming reaction. At this time, since the second reforming section blocks radiation heat transfer from the SOFC to the first reforming section, the temperature of the first reforming section is lower than the temperature of the second reforming section.

  3b is an electrolyte made of a solid oxide. Gas exchange and the like are appropriately performed using piping or the like.

  If the heat required for the reforming reaction cannot be provided by the SOFC exhaust heat alone, such as when the operating conditions fluctuate, the burner 1 burns kerosene with oxygen-containing gas (here, air), and the combustion heat is converted into a reformer. To make up for the shortage. The combustion exhaust is further used as necessary to be discharged to the outside.

  The burner can be controlled, for example, by continuously monitoring the temperature of the reforming catalyst and performing ON / OFF control so that the temperature becomes a predetermined value or more.

  Each supply gas is appropriately preheated as necessary and then supplied to the reformer or SOFC.

[Example 2]
FIG. 2 is a schematic diagram showing an internal reforming SOFC of the present embodiment. In Example 1, the inside of the cylindrical SOFC is the anode and the outside is the cathode. In this example, the inside is the cathode and the outside is the anode. Accordingly, the arrangement of the gas conduits is different from that of the first embodiment. Except this, it is the same as that of Example 1, and the same effect as Example 1 is acquired.

  The indirect internal reforming SOFC of the present invention can be used for, for example, a stationary or moving power generation system and a cogeneration system.

It is a schematic diagram which shows an example of the indirect internal reforming SOFC of the present invention. It is a schematic diagram which shows another example of the indirect internal reforming type | mold SOFC of this invention.

Explanation of symbols

1: Burner 2: Reformer 2a: First reformer 2b: Second reformer 3: SOFC
3a: anode electrode 3b: solid oxide electrolyte 3c: cathode electrode 4: SOFC stack 5: reforming material preheater

Claims (4)

A reformer capable of reforming kerosene, a solid oxide fuel cell fueled by a reformed gas obtained from the reformer, and a burner for heating the reformer,
The reformer is disposed between the solid oxide fuel cell and the burner;
The reformer has a first reforming section and a second reforming section communicating with each other;
Regarding the flow of the reformed gas, the first reforming section is located upstream and the second reforming section is located downstream,
The second reforming section is disposed at a position that receives heat radiation from the solid oxide fuel cell and blocks heat radiation from the solid oxide fuel cell to the first reforming section. Indirect internal reforming type solid oxide fuel cell ,
Further, it has a reforming material preheater directly connected to the reformer inlet for vaporizing, preheating and mixing kerosene and water.
Indirect internal reforming type solid oxide fuel cell . The first reformer and the second indirect internal reforming-type solid oxide fuel cell according to claim 1, wherein the reforming catalyst comprises a reforming catalyst having a kerosene oxidative activity filled in the reforming section. The indirect internal reforming solid oxide fuel cell according to claim 1 or 2, wherein the burner is a burner that burns kerosene. 3. The indirect internal reforming solid oxide fuel cell according to claim 1, wherein the burner is a surface combustion burner that is disposed with a combustion surface on the lower side and burns kerosene. 4.

Images