JP2003229163A - Back-up reformer for solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a back-up reformer for a solid oxide fuel cell which eliminates carbon precipitation at piping or a fuel cell electrode of the solid oxide fuel cell by effectively eliminating hydrocarbons having more than two carbon atoms in a molecule from fuel to be guided into the solid oxide fuel cell. <P>SOLUTION: The back-up reformer for removing hydrocarbon with more than two carbon atoms in a molecule from the fuel guided into the solid oxide fuel cell filled with reforming catalyst by a steam reforming method is so made to eliminate hydrocarbons having more than two carbon atoms in a molecule from the fuel cell with the use of exhaust air of the fuel cell as a necessary heating source. As the heating source, exhaust fuel and combustion gas of the both can also be utilized in addition to the exhaust air. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-reformer for a solid oxide fuel cell, and more specifically, a hydrocarbon to be introduced into the solid oxide fuel cell from which C ₂ or more hydrocarbons are removed. The present invention relates to a solid oxide fuel cell pre-reformer for producing a reformed gas.

[0002]

2. Description of the Related Art Solid Oxide Fuel Cell
el Cells: hereinafter abbreviated as SOFC as appropriate) is characterized in that an oxide ion (O ²⁻ ) conductor is used as a solid electrolyte, and a fuel electrode and an air electrode (or an oxygen electrode, with an oxygen ion between the solid electrolytes). Both electrodes (hereinafter appropriately referred to as air electrode) are arranged. During the operation, electric power is taken out by supplying a fuel to the fuel electrode side and supplying an oxidizing agent such as air, oxygen-enriched air and oxygen to the air electrode side to cause an electrochemical reaction.

FIG. 1 is a view for explaining the arrangement relationship between a solid electrolyte (= solid oxide electrolyte), a fuel electrode, and an air electrode in an SOFC unit cell and the operating principle thereof. A unit cell is configured by arranging a fuel electrode and an air electrode with a solid oxide electrolyte sandwiched therebetween. The air introduced into the air electrode becomes oxide ions (O ²⁻ ) at the air electrode, passes through the solid oxide electrolyte, and reaches the fuel electrode. Here, it reacts with the fuel introduced into the fuel electrode, emits electrons, and produces reaction products such as electricity and water. Spent air at the cathode is discharged as cathode off-gas, and spent fuel at the anode is discharged as anode off-gas, but in this specification, cathode off-gas is exhausted air and anode off-gas is exhausted fuel. Is called.

2 to 3 are schematic views showing an example of a flat plate type SOFC. The SOFC includes a cylindrical system and an integral laminated system, but in principle, it is the same as the flat plate system. 2 shows the case of the self-supporting membrane type, and FIG. 3 shows the case of the supporting membrane type. 2 to 3 show the case of a single battery,
Since the voltage of one unit cell is low, it is usually configured by stacking a plurality of unit cells. Note that a structure in which a plurality of unit cells are stacked is referred to as a stack or an SOFC stack in this specification and the drawings. In addition, although some of the materials used are shown in FIGS. 2 to 3, this is shown as an example.

As shown in FIG. 2, in the case of the self-supporting membrane type, the sealing material and the separator are sequentially arranged above the unit cell, and the separator, the sealing material and the separator are sequentially arranged below the unit cell,
These are densely stacked and configured. In the free-standing membrane type, the solid oxide electrolyte membrane itself holds its structure. Therefore, it is necessary to increase the thickness of the solid oxide electrolyte membrane itself, and the thickness is usually 100 μm.
Composed thick and thick. The operating temperature is 800 ~
A high temperature field of over 1000 ° C. is formed in the system, which is as high as around 1000 ° C. For this reason, the constituent materials are limited to expensive heat-resistant alloys and ceramics, and in the case of ceramics, there is a problem such as cracking due to the temperature difference in the stack. Becomes thicker and the SOFC system becomes larger.

On the other hand, as shown in FIG. 3, in the case of the support membrane type, the unit cell is held in the frame of the spacer, and the bonding material, the cell support, the spacer and the separator are sequentially arranged on the upper part thereof. A bonding material, a cell support, a spacer, and a separator are sequentially arranged in the lower part of the unit cell, but the illustration of those members is omitted in FIG. In the support membrane type, a material such as LaGaO ₃ based or zirconia based material is used as the solid oxide electrolyte membrane to form a thin film thickness of, for example, about 10 μm, and the solid oxide electrolyte membrane is supported by a thick fuel electrode. Is configured.

The present inventors have made such a support film type SOF.
We are paying particular attention to C and proceeding with its development, and have obtained some results so far (Japanese Patent Application No. 2001-176739).
etc). In the supporting membrane type, since the solid oxide electrolyte membrane can be made thin, it can be operated at a lower temperature than in the case of the self-supporting membrane type, and it is in the range of about 650 to 850 ° C, for example, about 750 ° C. Can operate at low temperatures. For this reason, there are various advantages that an inexpensive material such as stainless steel can be used as the constituent material and the size can be reduced.

In SOFC, not only hydrogen but also methane and CO are used as fuels. When city gas or LP gas is used, they are reformed and used. There are a steam reforming method and a partial combustion method as a hydrocarbon reforming method, and when the steam reforming method is applied to the reforming, it is common to perform internal reforming on the fuel electrode. However, if the fuel contains hydrocarbons other than methane, that is, hydrocarbons having a carbon number of C ₂ or more, such as ethane, ethylene, propane, butane, carbon is generated in the SOFC piping and fuel electrode, and this produces electricity. It hinders the chemical reaction and deteriorates the battery performance.

These problems are fatal in SOFCs that are repeatedly operated for a long period of time, but city gas,
Fuels such as LP gas, natural gas, kerosene, and gasoline contain hydrocarbons other than methane, that is, C ₂ or more hydrocarbons. For example, in city gas 13A, as an example, in addition to methane 88.5%, ethane 4.6
%, Propane 5.4%, butane 1.5% (% is vol
%, The same applies hereinafter), and in addition to methane, which is the main component, about 11.5% of C ₂ -C ₄ hydrocarbons are also contained. Therefore, in order to use these as SOFC fuels, it is necessary to reform those hydrocarbons and remove C ₂ or more hydrocarbons.

In the steam reforming method and the partial combustion method, hydrocarbons are
It is a technology that converts hydrogen into a reformed gas that contains carbon as a main component.
When the hydrogen is, for example, methane, the steam reforming reaction is
Formula: CH_Four+ H₂O = 3H₂Shown as + CO. By the way
However, in SOFC, not only hydrogen but also methane
Since carbon oxide is also a fuel, the fuel to be introduced into SOFC is
C ₂It suffices if the above hydrocarbons are removed, and hydrogen is mainly
It is not necessary to reform to the reformed gas as a component.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts and problems.
By using the steam reforming method or the partial combustion reforming method from the fuel introduced into, the hydrocarbons other than methane, that is, the hydrocarbons having C ₂ or more are reformed and the hydrocarbons other than methane are eliminated. An object of the present invention is to provide a pre-reformer for a solid oxide fuel cell.

Here, in the pre-reformer by the steam reforming method, heating is usually required to accelerate the reforming reaction, but the heating amount depends on the amount of hydrocarbons having C ₂ or more in the fuel. The endothermic reaction occurs when the amount of C ₂ or more hydrocarbons is small and the exothermic reaction occurs when the amount of C ₂ or more hydrocarbons is large. That is, the conversion reaction of C ₂ or more hydrocarbons to methane is an exothermic reaction, whereas the conversion reaction of methane to hydrogen, carbon monoxide, and carbon dioxide is an endothermic reaction. When the amount of hydrocarbons having C ₂ or more is large, such as in the above, an exothermic reaction occurs as a whole.

On the other hand, as described above, the SOFC generates heat during operation, and its operating temperature is lower than that of the self-supporting membrane type even with the supporting membrane type, but it is still high. Therefore, in the present invention, when heating is required to accelerate the reforming reaction as described above, the heat generated by the SOFC is skillfully used as a heating source to generate C ₂ or more from the SOFC fuel. An object of the present invention is to provide a pre-reformer for producing a reformed gas from which hydrocarbons have been removed.

[0014]

The present invention provides (1) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, said pre-reforming Is a pre-reformer by a steam reforming method filled with a reforming catalyst, and uses exhaust air of a fuel cell as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. A pre-reformer for a solid oxide fuel cell is provided.

The present invention is (2) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer comprising a reforming catalyst. A solid state reforming device which is a pre-reformer filled with a steam reforming method and which uses an exhaust fuel of a fuel cell as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. A pre-reformer for an oxide fuel cell is provided.

The present invention is (3) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer comprising a reforming catalyst. It is a pre-reformer by a filled steam reforming method, and uses exhaust air and exhaust fuel of a fuel cell as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. A pre-reformer for a solid oxide fuel cell is provided.

The present invention is (4) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer comprises a reforming catalyst. It is a pre-reformer by a filled steam reforming method, and uses a combustion gas obtained by burning the exhaust fuel of a fuel cell with exhaust air as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. A pre-reformer for a solid oxide fuel cell is provided.

The present invention is (5) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer comprises a reforming catalyst. It is a pre-reformer by a filled steam reforming method, and by preheating water into steam and preheating the fuel by preheating and introducing a mixed gas of both into the prereformer. Provided is a pre-reformer for a solid oxide fuel cell, which is characterized in that C ₂ or more hydrocarbons are eliminated from a fuel.

The present invention provides (6) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer comprising a reforming catalyst. It is a pre-reformer by the filled steam reforming method, and a part of the exhaust fuel from the fuel cell is recycled and mixed with the fuel to react with it to eliminate hydrocarbons having C ₂ or more. A pre-reformer for a solid oxide fuel cell is provided.

The present invention (7) is a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer comprises a reforming catalyst. It is a pre-reformer filled with a steam reforming method, and is capable of eliminating C ₂ or more hydrocarbons from the fuel by utilizing the heat of the reforming reaction without using a heating source. A pre-reformer for a solid oxide fuel cell, which is characterized.

The present invention is (8) a pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer is filled with an oxidation catalyst. For a solid oxide fuel cell, characterized in that it is a pre-reformer by the partial combustion reforming method described above, wherein the fuel is partially combusted with air so as to eliminate hydrocarbons of C ₂ or more. A pre-reformer is provided.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a pre-reformer for producing a pre-reformed gas obtained by removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell. That is, with respect to the fuel to be introduced into the solid oxide fuel cell, a preliminary reformation in which C ₂ or more hydrocarbons are eliminated and removed from the fuel before the fuel is supplied to the fuel electrode side of the solid oxide fuel cell. It is a pre-reformer for producing quality gas.

The pre-reformer is filled with a pre-reforming catalyst when the steam reforming method is used, and is filled with an oxidation catalyst when the partial combustion reforming method is used. The reforming catalyst in the case of the steam reforming method is not particularly limited as long as it is a catalyst that can remove and remove C ₂ or more hydrocarbons from the fuel, and for example Ni Ni
System catalyst (for example, a catalyst in which Ni is supported on alumina), Ru
Examples thereof include a system catalyst (for example, a catalyst in which Ru is supported on alumina).

As the fuel, gas fuels such as city gas, LP gas and natural gas, and liquid fuels such as kerosene, gasoline and alcohols are used. When modifying them in the pre-reformer, the methane to produce pre-reforming gas, hydrogen, in addition to carbon monoxide, carbon dioxide, and water vapor is contained, etc., ethane other, C ₂ or more hydrocarbons Since hydrogen has been removed, carbon is prevented from being deposited on the piping leading to the SOFC stack and the fuel electrode.

When the pre-reformer is a pre-reformer using a steam reforming method, it is necessary to use exhaust oxidant, exhaust fuel, or both exhausted from SOFC as a heating source required for reforming. Characterize. A combustion gas obtained by burning the exhaust fuel with an exhaust oxidant may be used as the heating source. The temperature of the reforming catalyst layer during the operation of the pre-reformer is preferably in the range of about 300 to 600 ° C., and the S / C ratio is not particularly limited, but is 1.5 to 6.0. It is preferably in the range.

As described above, in the pre-reformer by the steam reforming method, heating is usually required to accelerate the reforming reaction, but the heating amount is the amount of hydrocarbons of C ₂ or more in the fuel. It depends on how. The conversion reaction of methane to hydrogen, carbon monoxide, and carbon dioxide is an endothermic reaction, whereas the conversion reaction of C ₂ or more hydrocarbons to methane is an exothermic reaction. If there are a large amount of C ₂ or more hydrocarbons, the reaction will be exothermic as a whole.

That is, in the pre-reformer by the steam reforming method, when the fuel to be reformed is, for example, city gas, the amount of hydrocarbons having C ₂ or more in the city gas is smaller than that of LP gas, etc. _The endothermic amount due to the conversion of methane into hydrogen, carbon monoxide, and carbon dioxide becomes dominant rather than the exothermic amount due to the conversion of _two or more hydrocarbons into methane, and the endothermic amount becomes overall. When there are a large amount of hydrocarbons having C ₂ or more, such as LP gas, heat is generated as a whole. Therefore, the C ₂ in the fuel to be preliminarily reformed
Depending on the above-mentioned amount of hydrocarbons, the heating by the heating source is unnecessary or can be reduced.

On the other hand, in the case where the pre-reformer is a pre-reformer based on the partial combustion reforming method, since partial oxidation reaction is utilized, heating is not usually required, but auxiliary heating may be used. Good. According to the partial combustion reforming method, the air ratio λ (the amount of dry air actually supplied to the theoretical minimum amount of air required for complete combustion of fuel) is operated at less than 1. The oxidation catalyst packed in the pre-reformer is not particularly limited as long as it is a catalyst that can partially oxidize the fuel, and for example, a noble metal catalyst such as platinum or palladium is used. The noble metal catalyst is used by being supported on a carrier such as alumina.

4 to 7 are views for explaining an example of the embodiment of the pre-reformer by the steam reforming method. In the embodiment of FIGS. 4-5,
Water is supplied together with the fuel to the pre-reformer filled with the reforming catalyst, and the two are reacted with each other to eliminate C ₂ or more hydrocarbons and generate the removed pre-reformed gas. Either or both of the exhaust air and the exhaust fuel from the SOFC stack are used as the heating source. A combustion gas obtained by burning exhaust fuel with exhaust air can also be used as the heating source. FIG. 5 shows this case.

The temperatures of the exhaust air and the exhaust fuel from the SOFC stack are as high as the temperature of the SOFC stack, and the combustion gases of both are even higher.
It can supply the heat required for pre-reforming. The water supplied to the pre-reformer may be heated in advance and supplied as steam, or may be heated in the pre-reformer to form steam. Of these, when water is preheated and supplied as steam, the fuel may also be preheated and preheated, and the mixed gas of both may be introduced into the prereformer.

FIG. 6 also shows the case where the pre-reformer is based on the steam reforming method. As a heating source, either or both of exhaust air and exhaust fuel from the SOFC stack, or exhaust fuel is exhaust air. This is a mode in which the combustion gas that is burned is used, part of the exhaust fuel from the SOFC stack is recycled, and this is mixed with the fuel for heating. In this case, the exhaust fuel is SOFC
Since it contains steam generated in the stack, it is also used as a steam source for pre-reforming.

In the mode in which a part of the exhaust fuel is recycled as shown in FIG. 6, the temperature of the exhaust fuel is as high as the temperature of the SOFC stack, and in addition, the exhaust fuel contains water vapor generated in the SOFC stack. Therefore, the amount of heat and steam required in the pre-reformer can be covered only by the recycled exhaust fuel. In this case, by increasing the recycling rate of the exhaust fuel, the amount of heat and the amount of steam required for pre-reforming can be adjusted, and a separate heating source is not required. FIG. 7 shows a mode in this case.

8 to 9 are views for explaining an example of the embodiment of the pre-reformer by the partial combustion reforming method. An oxidant is supplied together with the fuel to a pre-reformer filled with an oxidation catalyst, and both are reacted to generate a pre-reformed gas from which C ₂ or more hydrocarbons have been removed. In the case of the partial combustion reforming method, the temperature rises because it is basically a combustion reaction. Therefore, heating may be performed with a heating source, but heating is not essential. As the oxidant, in addition to air, oxygen-enriched air, oxygen and the like can be used.

FIG. 8A shows the case of no heating.
(B) shows the case of heating. As the heat source in the embodiment of FIG. 8B, one or both of exhaust air and exhaust fuel from the SOFC stack are used. A combustion gas obtained by burning exhaust fuel with exhaust air may be used as the heating source.

FIG. 9 shows an embodiment in which the exhaust air from the SOFC stack is recycled and mixed with the fuel to be reformed for use. As a result, oxygen in the exhaust air is used as oxygen for partial combustion of fuel. In this case, it is possible to eliminate the need to supply new air by increasing the recycling rate of exhaust air.

As described above, in this pre-reformer, heating may or may not be necessary. When heating is required, one of the exhaust air and the exhaust fuel from the SOFC stack is used as a heating source. Both, or a combustion gas obtained by burning exhaust fuel with exhaust air is used. For this reason,
By arranging the pre-reformer in the vicinity of the SOFC stack arranged in the heat insulating container and in the heat insulating container, the heat can be used more efficiently and easily. 10 to 11 are diagrams for explaining this aspect example. As the heat insulating material constituting the heat insulating container, glass wool, slag wool, various refractory materials and other appropriate materials are used.

FIG. 10 shows an embodiment in which the pre-reformer is incorporated with an SOFC stack and a heat exchanger that utilizes combustion gas obtained by mixing and combusting exhaust air discharged from the SOFC stack and exhaust fuel. As shown in FIG. 10, an SOFC stack, a heat exchanger (catalytic combustion integrated heat exchanger including a first heat exchanger, a catalyst combustion layer, and a second heat exchanger) and a pre-reformer are sequentially installed in the heat insulating container. It has been incorporated. In addition,
10, the pre-reformer corresponds to the case where the pre-reformer is configured as shown in FIG. 5, and the fuel mixed with water is passed through the reforming catalyst of the pre-reformer. Is shown as a line.

FIG. 11 shows a case where a part of the exhaust fuel from the SOFC stack is recycled as fuel. S
A part of the exhaust fuel from the OFC stack is branched, mixed with the fuel, pre-reformed, and reused as the fuel. In this case, the remaining exhaust fuel is combusted in the catalytic combustion layer of the heat exchanger integrated with catalytic combustion, and is used for heating the air supplied to the SOFC stack and the fuel having passed through the pre-reformer. Further, the pre-reformer corresponds to the case where it is configured as shown in FIG. 6 described above, and uses combustion gas of exhaust fuel and exhaust air as a heating source. The other points are the same as in the case of FIG.

[0039]

The present invention will be described in more detail based on the following examples, but it goes without saying that the present invention is not limited thereto. It should be noted that, in the related drawings, valves and the like are appropriately arranged in the pipes for each fluid, and temperature detection sensors are arranged at respective necessary locations, but their description is omitted.

Example 1 In this example, the pre-reformer shown in FIG. 12 was used. This device is a multi-cylindrical pre-reformer with a circular cross section. As shown in FIG. 12, a tubular heat exchanger (tubular water heater) is arranged in the center, and a reforming catalyst is filled around the heat exchanger to form a reforming catalyst layer. The off gas from the SOFC (SOFC exhaust gas) flows around the outer circumference of the water pipe of the tubular water heater to heat the water flowing in the pipe, and is discharged from the SOFC exhaust gas discharge pipe. In this example, a catalyst obtained by adding 5 mol% of La to Ni / Al ₂ O ₃ [catalyst in which Ni is supported on alumina: spherical (average diameter ≈ 2 mm)] was used as the reforming catalyst. The weight ratio of Ni to Al ₂ O ₃ is 5
It is 0:50.

Fuel [in FIG. 12, city gas (desulfurized)]
Is introduced from the introduction pipe, mixed with steam generated in the tubular water heater in the mixing section, and introduced into the reforming catalyst layer. Here, C ₂ or more hydrocarbons in the fuel are reformed and converted into hydrogen, carbon monoxide, carbon dioxide, and methane which is C ₁ hydrocarbon. This removes C _{2 and} higher hydrocarbons,
It is supplied to the SOFC fuel electrode as SOFC fuel.
The pre-reformer having the above structure was manufactured using SUS310S, including the piping.

The pre-reformer thus constructed was housed together with an actual SOFC stack in a heat-insulating container in which glass wool was placed, and a pre-reforming test was carried out using this pre-reformer. 5 kW DC power generation SOFC stack temperature = 750
C., as a heating source (SOFC exhaust gas in FIG. 12), the exhaust fuel from the SOFC stack is combusted with exhaust air, and the air and fuel introduced into the SOFC stack are 70%.
The combustion gas that was used to raise the temperature to 0 ° C. was used. Other test conditions are: fuel = city gas 13A (desulfurized), fuel utilization = 80%, oxidant = air, oxidant utilization = 30
%, S / C ratio = 2.0, space velocity (including water vapor) = 30
It was set to 00h- ¹ . Table 1 shows the composition, composition, and flow rate (NLM = Normal Liter per Minute) of the gas at each location.

[0043]

[Table 1]

FIG. 13 shows the results of this test. The horizontal axis represents time, the left vertical axis represents the gas concentration, and the right vertical axis represents the temperature of the pre-reformed gas from the pre-reformer at the outlet (reforming catalyst layer outlet). The temperature of the pre-reformed gas at the outlet of the pre-reformer was 395 ° C. from the beginning of the test, and remained almost constant even after 200 hours had passed.

Regarding the concentration of CH ₄ , after the start of the test,
Almost 53% with only slight vertical fluctuations at each measurement
Maintain the standard of. The H ₂ concentration is maintained at a level of about 30% with only a slight vertical fluctuation after the start of the test at each measurement. The concentration of CO ₂ was 14.6% from the beginning of the test and did not change even after more than 200 hours, and the components of CO and C _{2 to} C ₄ were scarcely contained from the beginning of the test.

Carbon (C) analysis was performed on the catalyst in the reforming catalyst layer after the test. As a result, carbon (C) was not detected. Further, the generated pre-reformed gas was heated to 700 ° C. and supplied to the SOFC stack, but carbon (C) was not deposited on the pipes and electrodes. Thus, according to the present invention, hydrocarbons of ethane or more, that is, hydrocarbons of C ₂ or more are extremely effectively removed, and carbon is deposited by these hydrocarbons, that is, pipes and SO before being introduced into the stack.
It is possible to eliminate carbon deposition at the fuel electrode of FC.

Example 2 A preliminary reforming test was conducted using the apparatus shown in FIG. As shown in the figure, the present apparatus is a cylindrical container, which is made of SUS310S including a pipe, and is filled with a reforming catalyst. The pre-reformer thus constructed was housed in a heat insulating container in which glass wool was placed, and a reforming test was carried out using this pre-reformer. 60% of the exhaust fuel from the actual SOFC stack (exhaust fuel recycling rate = 60%) was recycled and mixed into city gas (fuel) for reuse as SOFC fuel. Except this, it implemented on the same conditions as Example 1. The components, composition and flow rate of each gas are shown in Table 2, and are the same as those in Table 1 except for the flow rate of the recycled exhaust fuel (= recycled gas).

[0048]

[Table 2]

FIG. 15 is a diagram showing the results of this experiment.
The left vertical axis and the right vertical axis are the same as those in FIG. As shown in FIG. 15, the temperature at the outlet of the reforming catalyst layer was 5 from the beginning of the test.
The temperature was 30 ° C., which remained almost constant and did not change even after 240 hours. In this way, the recycled exhaust fuel has a high temperature because it is a gas after power generation.
Temperatures above 500 ° C are maintained.

CH_FourThe concentration of
A level of about 27% with only a slight fluctuation
I am maintaining. H₂As for the concentration of
It is almost 5 with only a slight up / down change each time when descending or measuring.
The level of 2% is maintained. CO ₂The concentration of
About 19% from the beginning, it does not change even if more than 240 hours have passed,
Furthermore, the CO concentration was 5% from the beginning of the test.
However, there is almost no change even after 240 hours. Special
To C₂H₆, C₃H₈, N-C_FourH_Ten, I-C_FourH_TenSuch as C ₂
The above components were not detected from the beginning of the test
It was

As a result of carbon (C) analysis of the catalyst in the reforming catalyst layer after the test, carbon (C) was not detected. In addition, the generated pre-reformed gas is heated to 750 ° C.
It was supplied to the FC stack, but there was no carbon (C) deposition on the pipes or electrodes. As described above, according to the present invention, hydrocarbons of ethane or higher, that is, hydrocarbons of C ₂ or higher are extremely effectively removed, and carbon is deposited by these hydrocarbons, that is, pipes before introduction into a stack or a fuel electrode of SOFC. It is possible to eliminate the carbon deposition at.

[0052]

According to the present invention, by arranging a pre-reformer for the fuel to be introduced into the SOFC in the SOFC stack, hydrocarbons of ethane or more, that is, C ₂ or more are extremely effectively removed. It is possible to eliminate carbon deposition due to C ₂ or more hydrocarbons, that is, carbon deposition in the pipe or SOFC fuel electrode before introduction into the stack. Further, since the present pre-reformer operates in a temperature range of about 300 to 600 ° C., it is very useful as a pre-reformer for SOFCs, especially in a support membrane type SOFC whose operating temperature is about 850 ° C. or less. is there.

[Brief description of drawings]

FIG. 1 is a view for explaining the arrangement relationship between a solid oxide electrolyte membrane, a fuel electrode, and an air electrode in an SOFC unit cell and the operating principle thereof.

FIG. 2 is a diagram schematically showing the structure of a flat plate type SOFC (freestanding membrane type).

FIG. 3 is a diagram schematically showing the structure of a flat plate type SOFC (supporting membrane type).

FIG. 4 is a diagram for explaining an aspect of a pre-reformer [in the case of steam reforming (No. 1)]

FIG. 5 is a diagram for explaining an aspect of a pre-reformer [in the case of steam reforming (part 2)]

FIG. 6 is a diagram for explaining an aspect of a pre-reformer [in the case of steam reforming (3)]

FIG. 7 is a diagram for explaining an aspect of a pre-reformer [in the case of steam reforming (Part 4)]

FIG. 8 is a diagram for explaining an aspect of a pre-reformer (in the case of partial combustion reforming).

FIG. 9 is a diagram for explaining an aspect of a pre-reformer (in the case of partial combustion reforming).

FIG. 10 is a diagram showing an embodiment of a solid oxide fuel cell system incorporating a pre-reformer according to the present invention.

FIG. 11 is a diagram showing an embodiment of a solid oxide fuel cell system incorporating a pre-reformer according to the present invention (when a part of exhaust fuel is recycled).

FIG. 12 is a diagram showing a pre-reformer used in Example 1.

FIG. 13 is a diagram showing the results of Example 1.

FIG. 14 is a diagram showing a pre-reformer used in Example 2.

FIG. 15 is a diagram showing the results of Example 2.

Claims (13)

[Claims] 1. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer being a steam reformer filled with a reforming catalyst. Solid oxide fuel cell, characterized in that it is a pre-reformer according to the method and uses exhaust air of a fuel cell as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. Pre-reformer for. 2. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer being a steam reformer filled with a reforming catalyst. Solid oxide fuel cell, characterized in that it is a pre-reformer according to the method of claim 1, and uses exhaust gas of a fuel cell as a heating source to eliminate hydrocarbons of C ₂ or more from the fuel. Pre-reformer for. 3. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer being a steam reformer filled with a reforming catalyst. Solid oxide which is a pre-reformer according to the method, and which uses exhaust air and exhaust fuel of a fuel cell as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. Pre-reformer for type fuel cells. 4. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer is a steam reformer filled with a reforming catalyst. Is a pre-reformer according to the method, and uses a combustion gas obtained by combusting exhaust fuel of a fuel cell with exhaust air as a heating source to eliminate C ₂ or more hydrocarbons from the fuel. A characteristic pre-reformer for a solid oxide fuel cell. 5. The solid oxidation according to claim 2, wherein the exhaust fuel is a residual exhaust fuel obtained by recycling a part of the exhaust fuel from the fuel cell as a fuel for the fuel cell. Pre-reformer for solid fuel cells. 6. From the fuel introduced into the solid oxide fuel cell
C₂It is a pre-reformer for removing the above hydrocarbons.
The pre-reformer has a steam reforming method filled with a reforming catalyst.
Is a pre-reformer, and water is preheated to steam
And preheat the fuel to preheat it and mix both
By introducing gas into the pre-reformer, C ₂
Characterized by eliminating the above hydrocarbons
Pre-reformer for solid oxide fuel cells. 7. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, the pre-reformer being a steam reformer filled with a reforming catalyst. Is a pre-reformer according to the method, and a part of exhaust fuel from a fuel cell is recycled and mixed with the fuel to react with it so that hydrocarbons having C ₂ or more are eliminated from the fuel. A pre-reformer for a solid oxide fuel cell, which is characterized in that: 8. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer is a steam reformer filled with a reforming catalyst. Solid-state oxidation according to the present invention, characterized in that the heat of the reforming reaction is utilized to eliminate C ₂ or more hydrocarbons from the fuel without using a heating source. Pre-reformer for solid fuel cells. 9. A pre-reformer for removing C ₂ or more hydrocarbons from a fuel introduced into a solid oxide fuel cell, wherein the pre-reformer is a partial combustion reformer filled with an oxidation catalyst. A pre-reformer for a solid oxide fuel cell, characterized in that it is a pre-reformer according to the method, wherein C ₂ or more hydrocarbons are eliminated by partially burning the fuel with air. 10. The solid oxide fuel cell pre-reformer according to claim 9, wherein the pre-reformer is supplementarily heated, and the heating source thereof is exhaust fuel and exhaust fuel of the fuel cell. A pre-reformer for a solid oxide fuel cell, characterized in that either one or both of the above are utilized. 11. The solid oxide fuel cell pre-reformer according to claim 9, wherein the pre-reformer is supplementarily heated, and the exhaust fuel of the fuel cell is exhaust air as a heating source. A pre-reformer for a solid oxide fuel cell, which is characterized in that it uses combustion gas burned in. 12. The fuel is city gas, LP gas, natural gas, kerosene, gasoline or alcohols.
12. The pre-reformer for a solid oxide fuel cell according to any one of 11 above. 13. The pre-reformer for a solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is a support membrane type solid oxide fuel cell.