JP2018006066A - System for fuel cell - Google Patents

Abstract

Provided is a fuel cell system capable of efficiently purifying unburned gas even when a hydrocarbon fuel is used as fuel for a fuel cell. A fuel cell system includes a fuel cell that uses a hydrocarbon-based fuel, and an exhaust processing unit that processes unburned gas discharged from the fuel cell. The exhaust treatment unit includes an HC reforming unit having a catalyst for reforming hydrocarbons arranged upstream in the exhaust gas flow direction, and a catalyst for combusting the reformed gas arranged downstream from the HC reforming unit. A reformed gas combustion section. The HC reforming section and the reformed gas combustion section are disposed on the same integral structure type carrier. [Selection] Figure 1

Description

  The present invention relates to a fuel cell system. More particularly, the present invention relates to a fuel cell system using a hydrocarbon fuel.

  Conventionally, a solid oxide fuel cell capable of achieving various objects has been proposed (see Patent Document 1). This solid oxide fuel cell is composed of a cell plate formed by sandwiching an electrolyte layer between a fuel electrode and an air electrode, and a fuel gas flow path through which fuel gas flows between the cell plate stacked with a gap therebetween The separator which forms is provided. The cell plate and the separator are each provided with a fuel gas supply opening, an air supply opening, and an exhaust opening that communicate with each other and form a fuel gas supply path, an air supply path, and an exhaust flow path along the stacking direction. Combustion means is provided at the outlet of the fuel gas flow path between the cell plate and the separator to burn the fuel gas that has not burned while passing through the fuel gas flow path while maintaining the distance between the cell plate and the separator. Built-in in communication with the exhaust passage.

Patent No. 3972240

  However, the solid oxide fuel cell described in Patent Document 1 is excellent in purification of unburned gas when hydrogen is used as the fuel for the fuel cell. However, a hydrocarbon-based fuel is used as the fuel for the fuel cell. There was room for improvement in the purification of unburned gas when used.

  The present invention has been made in view of such problems of the prior art. An object of the present invention is to provide a fuel cell system capable of efficiently purifying unburned gas even when a hydrocarbon fuel is used as a fuel for a fuel cell.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, in a predetermined exhaust treatment unit, an HC reforming unit having a catalyst for reforming hydrocarbons is arranged upstream in the exhaust gas flow direction, and the reformed gas is burned downstream from the HC reforming unit. It has been found that the above object can be achieved by disposing a reformed gas combustion section having a catalyst to perform the present invention, and the present invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where a hydrocarbon fuel is used as a fuel of a fuel cell, the system for fuel cells which can purify | clean an unburned gas efficiently can be provided.

FIG. 1 is an explanatory diagram showing an outline of a fuel cell system according to a first embodiment of the present invention. FIG. 2 is a perspective view showing an outline of the exhaust processing section shown in FIG. FIG. 3 is a front view showing an outline of a portion surrounded by a surrounding line III of the exhaust treatment unit shown in FIG. FIG. 4 is an explanatory diagram showing an outline of the catalyst layer of the HC reforming unit shown in FIG. FIG. 5 is an explanatory diagram showing an outline of the catalyst layer of the reformed gas combustion section shown in FIG. FIG. 6 is an explanatory diagram showing an outline of a fuel cell system according to the second embodiment of the present invention. FIG. 7 is a perspective view showing an outline of the exhaust processing section shown in FIG.

  Hereinafter, a fuel cell system according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, the dimension ratio of drawing quoted by the following embodiment is exaggerated on account of description, and may differ from an actual ratio.

<First Embodiment>
First, a fuel cell system according to a first embodiment of the present invention will be described. FIG. 1 is an explanatory diagram showing an outline of a fuel cell system according to the first embodiment. FIG. 2 is a perspective view showing an outline of the exhaust processing section shown in FIG. Further, FIG. 3 is a front view showing an outline of a portion surrounded by an enveloping line III of the exhaust processing unit shown in FIG. FIG. 4 is an explanatory diagram showing an outline of the catalyst layer of the HC reforming section shown in FIG. Further, FIG. 5 is an explanatory diagram showing an outline of the catalyst layer of the reformed gas combustion section shown in FIG.

  As shown in FIGS. 1 and 2, the fuel cell system 1 of the present embodiment includes a fuel cell 10 and an exhaust treatment unit 20. The exhaust processing unit 20 is disposed in the exhaust pipe 11 connected to the fuel cell 10.

  The fuel cell 10 is not particularly limited as long as it uses a hydrocarbon-based fuel as a fuel. For example, a solid oxide in which an electrolyte such as yttria-stabilized zirconia is sandwiched between an anode and a cathode. A fuel cell can be applied. Examples of the hydrocarbon fuel include hydrocarbons composed of carbon and hydrogen, and oxygen-containing hydrocarbons containing carbon, hydrogen, and oxygen. Moreover, these may contain water. Specific examples of the oxygen-containing hydrocarbon include alcohol-containing fuel. Examples of the alcohol-containing fuel include those containing ethanol. Typically, a mixture of ethanol and water can be used.

Further, as the exhaust processing unit 20, the unburned gas discharged from the fuel cell 10 is processed, and the HC reforming unit 21 disposed on the upstream side along the exhaust gas flow direction indicated by the arrow X in the figure. And a reformed gas combustion section 23 disposed downstream of the HC reforming section 21. Here, the HC reforming unit 21 has a catalyst for reforming hydrocarbons (not shown). The reformed gas combustion unit 23 has a catalyst for burning the reformed gas (not shown). Examples of the unburned gas include hydrogen (H ₂ ), carbon monoxide (CO), hydrocarbon (HC) such as methane (CH ₄ ) and ethane (C ₂ H ₄ ). In addition, the catalyst of the HC reforming unit 21 having a catalyst for reforming hydrocarbons has higher reactivity for hydrocarbon reforming than the catalyst of the reformed gas combustion unit 23 having a catalyst for burning reformed gas. . Further, the reformed gas combusting unit 23 includes hydrogen (H ₂ ) contained in unburned gas in addition to hydrogen (H ₂ ) and carbon monoxide (CO) generated by the reforming reaction in the HC reforming unit 21. The reactivity of carbon monoxide (CO) combustion is high. Although not shown, a fuel cell using a hydrocarbon-based fuel may have a fuel reformer that advances a steam reforming reaction in the previous stage. In this case, unreformed gas that has not been completely reformed by the fuel reformer may be included in the unburned gas, but this can also be processed.

  Furthermore, the HC reforming unit 21 and the reformed gas combustion unit 23 are disposed on the same monolithic structure type carrier 211 (231). As the monolithic structure type carrier 211 (231), for example, a honeycomb carrier made of a heat resistant material such as a ceramic such as cordierite or a metal such as ferritic stainless steel can be applied.

  Further, the reformed gas combustion unit 23 is disposed directly below the HC reforming unit 21 along the exhaust gas flow direction indicated by the arrow X in the drawing.

  Further, as shown in FIG. 3, a catalyst layer 211 </ b> B is formed in the exhaust gas passage 211 </ b> A of the integral structure carrier 211.

  As shown in FIG. 4, the catalyst layer 211B of the HC reforming unit 21 shown in FIG. 2 has a catalyst 213 for reforming at least hydrocarbons. The catalyst 213 includes, for example, a catalyst metal 215 containing rhodium and a base material 217 that supports the catalyst metal 215.

  Further, as shown in FIG. 5, the catalyst layer 231B of the reformed gas combustion unit 23 shown in FIG. 2 has at least a catalyst 233 for burning the reformed gas. The catalyst 233 includes, for example, a catalyst metal 235 containing at least one of platinum and palladium, and a base material 237 carrying the catalyst metal 235.

  As described above, in the exhaust treatment section, an HC reforming section having a catalyst for reforming hydrocarbons is arranged upstream in the exhaust gas flow direction, and the reformed gas is burned downstream from the HC reforming section. By arranging a reformed gas combustion section having a catalyst to perform, even when a hydrocarbon fuel, preferably an alcohol-containing fuel, is used as fuel for the fuel cell, unburned gas can be purified efficiently. it can. This also has a secondary advantage that the size of the exhaust processing section can be reduced. Furthermore, this has a secondary advantage that the amount of catalyst metal used can be reduced. This also has the secondary advantage that the cost due to the use of the catalyst metal can be reduced.

  At present, we believe that unburned gas can be efficiently purified by the following mechanism.

For example, in an unburned gas of a fuel containing an alcohol such as ethanol, methane (CH ₄ ), ethane (C ₂ H ₄ ), and the like are compared with hydrogen (H ₂ ) and carbon monoxide (CO). The reactivity of carbon hydrogen (HC) is low. Therefore, by disposing the HC reforming unit on the upstream side in the exhaust gas flow direction that is close to the fuel cell and relatively high in temperature, in the HC reforming unit, methane (CH ₄ ) or ethane, which is an endothermic reaction, is disposed. Steam reforming reaction of hydrocarbon (HC) such as (C ₂ H ₄ ) (for example, CH ₄ + H ₂ O → CO + 3H ₂ ) can be promoted, and methane (CH ₄ ), ethane (C ₂ H ₄ ), etc. It is possible to improve the purification performance of hydrocarbons (HC). In addition, the water vapor | steam in a steam reforming reaction can utilize what is produced | generated in a fuel cell, or a fuel origin, for example.

Although the reactivity to hydrocarbons (HC) such as methane (CH ₄ ) and ethane (C ₂ H ₄ ) is lower than that of the HC reforming section, methane (CH ₄ ) and ethane (C _Since hydrocarbons (HC) such as ₂ H ₄ ) can be reformed, the reaction area of hydrocarbons (HC) such as methane (CH ₄ ) and ethane (C ₂ H ₄ ) with low reactivity is increased, The purification performance of hydrocarbons (HC) such as methane (CH ₄ ) and ethane (C ₂ H ₄ ) can be improved.

Furthermore, in the unburned gas of the alcohol-containing fuel, hydrogen (H ₂ ) and carbon monoxide (CO) are compared with hydrocarbons (HC) such as methane (CH ₄ ) and ethane (C ₂ H ₄ ). High reactivity. Therefore, these can be purified also in the reformed gas combustion section arranged on the downstream side of the HC reforming section.

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the scope of the present invention.

  Further, as described above, it is preferable that the HC reforming section and the reformed gas combustion section are disposed on the same monolithic structure type carrier. With such a configuration, the reformed gas from the HC reforming unit can be efficiently purified in the reformed gas combustion unit.

  At present, the reformed gas can be efficiently purified by the following mechanism.

  For example, since the heat generated in the reformed gas combustion section can be used for the reaction in the upstream HC reforming section via the monolithic structure type carrier, the reformed gas can be efficiently generated in the HC reforming section. .

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the scope of the present invention.

  Needless to say, the scope of the present invention includes a case where the HC reforming section and the reformed gas combustion section are disposed on separate integral structure type carriers.

  Furthermore, as described above, it is preferable that the reformed gas combustion section is disposed directly below the HC reforming section along the exhaust gas flow direction. With such a configuration, the reformed gas from the HC reforming unit can be efficiently purified in the reformed gas combustion unit.

  At present, the reformed gas can be efficiently purified by the following mechanism.

  For example, since the heat generated in the reformed gas combustion section can be used for the reaction in the upstream HC reforming section via the monolithic structure type carrier, the reformed gas can be efficiently generated in the HC reforming section. .

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the scope of the present invention.

  Needless to say, the scope of the present invention includes a case where the reformed gas combustion section is not disposed directly below the HC reforming section along the exhaust gas flow direction. When the reformed gas combustion section is not disposed immediately below the HC reforming section along the exhaust gas flow direction, for example, other reactions proceed between the HC reforming section and the reformed gas combustion section. This is a case of having another reaction part, an oxidant gas addition part for adding an oxidant gas such as air, and a heating part.

  Further, as described above, it is preferable that the catalyst for reforming the hydrocarbon in the HC reforming portion includes a catalyst metal containing at least rhodium (Rh) and a base material supporting the catalyst metal. By setting it as such a structure, it becomes easy to advance the steam reforming reaction mentioned above. As a result, even when a hydrocarbon fuel, preferably an alcohol-containing fuel, is used as the fuel for the fuel cell, the unburned gas can be purified efficiently.

  The catalyst metal in the catalyst for reforming the hydrocarbon in the HC reforming portion is not limited to this, but rhodium (Rh), platinum (Pt), palladium (Pd), nickel (Ni), iron (Fe), cobalt (Co), ruthenium (Ru), iridium (Ir), osmium (Os), or any combination thereof can be applied, but those containing at least rhodium (Rh) are applied. It is preferable.

  In addition, as the base material in the catalyst for reforming the hydrocarbon in the HC reforming section, for example, alumina, zirconia, silica, titania, ceria, or the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type. In particular, it is preferable to apply alumina that can ensure a high specific surface area.

Further, as described above, the catalyst for burning the reformed gas in the reformed gas combustion section includes a catalyst metal containing at least one of platinum (Pt) and palladium (Pd), and a base material supporting the catalyst metal. It is preferable. With such a configuration, combustion of hydrocarbons (HC) such as hydrogen (H ₂ ), carbon monoxide (CO), and ethane (C ₂ H ₄ ) described above easily proceeds. As a result, even when a hydrocarbon fuel, preferably an alcohol-containing fuel, is used as the fuel for the fuel cell, the unburned gas can be purified efficiently.

  The catalyst metal in the reformed gas combustion section is not limited to this, but palladium (Pd), platinum (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) or osmium (Os) ) Or an arbitrary combination thereof, but it is preferable to apply at least one of platinum (Pt) and palladium (Pd).

In addition, when both platinum (Pt) and palladium (Pd) are applied, platinum (Pt) effective for burning hydrogen (H ₂ ) and carbon monoxide (CO) in the exhaust gas flow direction in particular. In particular, in addition to carbon monoxide (CO) and hydrogen (H ₂ ), palladium (Pd), which is effective for combustion of methane (CH ₄ ), is downstream along the exhaust gas flow direction. It is preferable to arrange in. Since the steam reforming reaction in the HC reforming part is an endothermic reaction, the temperature of the exhaust gas at the inlet of the reformed gas combustion part is lowered, but hydrogen (H ₂ ) and carbon monoxide (CO ), The temperature of palladium (Pd) rises due to the heat of combustion, and more effectively burns methane (CH ₄ ) in addition to carbon monoxide (CO) and hydrogen (H ₂ ). And unburned gas can be purified efficiently. However, the present invention is not limited to such an arrangement.

  Further, for example, alumina, zirconia, silica, titania, ceria and the like can be used as the base material in the reformed gas combustion section. These may be used individually by 1 type and may be used in combination of 2 or more type. In particular, it is preferable to apply alumina that can ensure a high specific surface area.

  The base materials in the HC reforming section and the reformed gas combustion section may be the same or different.

<Second Embodiment>
Next, a fuel cell system according to a second embodiment of the present invention will be described. FIG. 6 is an explanatory diagram showing an outline of a fuel cell system according to the second embodiment. FIG. 7 is a perspective view showing an outline of the exhaust processing section shown in FIG. Moreover, about the thing equivalent to what was demonstrated in said embodiment, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

  As shown in FIGS. 6 and 7, in the fuel cell system 2 of the present embodiment, the HC reforming unit 21 and the reformed gas combustion unit 23 are arranged on separate integrated structure carriers (211, 231). The configuration is different from that of the first embodiment described above.

  As described above, in the exhaust treatment unit, the HC reforming unit having a catalyst for reforming hydrocarbons is disposed on the upstream monolithic support along the exhaust gas flow direction, and the downstream side of the HC reforming unit is disposed. Even if a hydrocarbon-based fuel, preferably an alcohol-containing fuel is used as the fuel for the fuel cell by disposing a reformed gas combustion section having a catalyst for burning the reformed gas on the monolithic structure type carrier, Unburned gas can be purified efficiently.

  At present, the reformed gas can be efficiently purified by the following mechanism.

  For example, as described above, even if the HC reforming section and the reformed gas combustion section are arranged on separate integrated structure type carriers, the reformed gas combustion section will be HC reformed along the exhaust gas flow direction. Because the thermal energy of the reformed gas generated in the HC reforming unit is lost or before the side reaction of the reformed gas occurs, the reformed gas is burned by the reformed gas. It can be burned in the part. Therefore, the reformed gas can be efficiently purified.

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the scope of the present invention.

  As mentioned above, although this invention was demonstrated by some embodiment, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

DESCRIPTION OF SYMBOLS 1, 2 Fuel cell system 10 Fuel cell 11 Exhaust pipe 20 Exhaust treatment part 21 HC reforming part 211 Monolithic structure type support 211A Exhaust gas flow path 211B Catalyst layer 213 Catalyst 215 Catalyst metal 217 Base material 23 Reformed gas combustion part 231 Monolithic structure type carrier 231B Catalyst layer 233 Catalyst 235 Catalyst metal 237 Base material

Claims (6)

A fuel cell using a hydrocarbon-based fuel, and an exhaust treatment unit for treating unburned gas discharged from the fuel cell,
The exhaust treatment unit is disposed on the upstream side in the exhaust gas flow direction and has an HC reforming unit having a catalyst for reforming hydrocarbons, and is disposed on the downstream side of the HC reforming unit and combusts the reformed gas. And a reformed gas combustion section having a catalyst.   2. The fuel cell system according to claim 1, wherein the HC reforming unit and the reformed gas combustion unit are disposed on the same monolithic structure type carrier. 3.   3. The fuel cell system according to claim 1, wherein the reformed gas combustion unit is disposed immediately below the HC reforming unit along an exhaust gas flow direction. 4.   The fuel cell system according to any one of claims 1 to 3, wherein the HC reforming section includes a catalyst metal containing at least rhodium and a base material supporting the catalyst metal.   The said reformed gas combustion part contains the catalyst metal containing at least one of platinum and palladium, and the base material which carry | supports the said catalyst metal, The statement of any one of Claims 1-4 characterized by the above-mentioned. Fuel cell system.   The fuel cell system according to any one of claims 1 to 5, wherein the hydrocarbon fuel is an alcohol-containing fuel.

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