JP5939501B2 - Gas decomposition apparatus, gas decomposition method, and gas decomposition power generation apparatus - Google Patents

Description

  The present invention relates to a gas decomposition apparatus, a gas decomposition method, and a gas decomposition power generation apparatus. More specifically, the present invention relates to a gas decomposition apparatus capable of efficiently decomposing gas in response to a change in gas concentration or a change in gas composition during the gas decomposition process.

  For example, various gas components are contained in biogas (volatile organic compound) generated in human waste processing and compost manufacturing processes. For example, ammonia gas is often included as a gas component that causes bad odor.

  The ammonia gas not only emits a bad odor but is also harmful to the human body, so it cannot be released as it is to the outside air. For this reason, the method (patent document 1) which isolate | separates ammonia gas and makes it contact with a hypobromite solution and a sulfuric acid, and the method (patent document 2) which carries out a combustion process using a catalyst may be employ | adopted. Many.

The ammonia gas can be decomposed and detoxified by a method using a chemical as described in Patent Document 1 or a combustion method as described in Patent Document 2. However, since these methods require chemicals and external energy, there is a problem that the running cost increases. Further, if a combustion method is employed, NO _x and CO ₂ may be generated, which may adversely affect the environment.

  As a technique for solving the above problem, a technique for electrochemically decomposing and detoxifying a gas using a gas decomposition element having a solid electrolyte as described in Patent Document 3 has been proposed. By using the above method, no harmful gas is generated, the apparatus can be downsized, and the running cost can be kept low.

JP-A-7-31966 Japanese Patent Laid-Open No. 7-116650 JP 2010-247033 A

  When the gas is decomposed using the solid electrolyte, the gas is decomposed while flowing along the anode electrode. For this reason, the density | concentration of the gas used as the decomposition | disassembly object falls according to the flow distance along a solid electrolyte layer.

  Conventionally, the catalyst has been uniformly blended at a constant rate over the entire anode electrode to which the gas flows and contacts. However, as the gas is decomposed, the concentration decreases or the composition changes. For this reason, the catalyst which has the optimal compounding quantity and composition cannot be made to act according to the gas concentration etc. which change with a flow. Therefore, it cannot be said that the ability of the gas decomposition element (MEA) is exhibited to the maximum.

For example, when ammonia gas is decomposed by the gas decomposition element including the solid electrolyte layer, a part of the ammonia gas (NH ₃ ) is decomposed as follows on or near the anode electrode surface.
<Anode reaction>
2NH ₃ → N ₂ + 3H ₂
The N ₂ is discharged as exhaust gas. When the oxygen conductive solid electrolyte is employed, the H ₂ combines with oxygen at the anode to generate water. On the other hand, when a proton conductive solid electrolyte is employed, the H ₂ is further decomposed at the anode to generate proton H ⁺ and an electron e ⁻ , and the proton H ⁺ is moved toward the cathode through the solid electrolyte. In combination with oxygen at the cathode, water is produced.

  That is, a gas in which hydrogen gas and ammonia gas are mixed is allowed to act on the anode electrode of the gas decomposition element. Moreover, in order to improve the decomposition efficiency of gas, the method of heating ammonia gas and hydrogenating a part of ammonia gas in a pre-process is also employ | adopted.

  As a catalyst component for decomposing the gas containing hydrogen gas and ammonia gas, a catalyst made of Ni—Fe is often employed. However, among the catalysts composed of Ni—Fe, the efficiency of decomposing ammonia gas is higher with the Fe catalyst, while the efficiency of decomposing hydrogen gas to generate water or proton is higher than that of the Ni catalyst. Is expensive. In the conventional gas decomposition apparatus, the Ni—Fe catalyst having a predetermined mixing ratio is uniformly mixed throughout the anode electrode. For this reason, it cannot be said that the ability of the gas decomposition element is fully exhibited.

In addition, biogas generated in human waste processing and compost manufacturing processes often includes various gas components in addition to the above-described ammonia gas. When decomposing a mixed gas containing ammonia gas and other gas components, the above-described catalyst for ammonia gas may not be able to sufficiently decompose gases other than ammonia gas. Further, when these gas components are harmless, they can be released to the atmosphere as they are, but when they are harmful or when they adversely affect the decomposition of ammonia gas, they need to be removed. For example, H ₂ S is harmful to the human body, and when water vapor coexists, the performance of the gas decomposition apparatus is reduced. Therefore, it is preferable to remove these gases before acting on the ammonia gas decomposition element.

  The invention of the present application provides a gas decomposition apparatus that solves the above-described problems and increases the gas decomposition efficiency by adopting an optimal catalyst in response to changes in gas concentration and composition in the decomposition process. This is the issue.

The present invention is a solid electrolyte layer, a first electrode layer provided on one side of the solid electrolyte layer, a second electrode layer provided on the other side of the solid electrolyte layer, and a first catalyst component. Gas decomposition that includes a plurality of gas decomposition elements including Fe and a catalyst containing Ni as the second catalyst component, and decomposes the gas containing ammonia by sequentially causing a gas including ammonia to act on the plurality of gas decomposition elements. It concerns the device . Each of the plurality of gas decomposition elements decomposes the gas containing ammonia in the first electrode layer into nitrogen and hydrogen, further decomposes the hydrogen into protons, and the protons pass through the solid electrolyte to the second electrode. at the electrode layer, and the pro tons and oxygen at the second electrode layer is intended to react to produce water. The catalyst is blended in the material constituting the first electrode layer, blended in the catalyst layer provided on the surface of the first electrode layer , or in the first electrode layer. It is added to the current collector provided adjacently along the first electrode layer. Regarding the mixing ratio of the first catalyst component and the second catalyst component of the catalyst in the plurality of gas decomposition elements, the one that causes the ammonia gas to act first is compared to the one that causes the gas containing ammonia to act later. The blending ratio of the first catalyst component is high and the blending ratio of the second catalyst component is set low.

The gas decomposition apparatus according to the present invention is applied to a gas containing ammonia. Further, the present invention can be applied to a gas containing other gas components in addition to ammonia gas .

  The material constituting the solid electrolyte layer is not particularly limited. For example, a gas decomposition apparatus can be configured by combining a plurality of types of gas decomposition elements including solid oxides, solid polymers, and the like. When working a solid electrolyte layer made of a solid oxide, oxygen ion conductive SSZ (scandium stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC (samarium stabilized zirconia), LSGM (lanthanum gallate), GDC (Gadria stabilized ceria) or the like can be employed. Further, a proton conductive solid electrolyte layer made of BYZ (yttrium-added barium zirconate), BCY (barium selete), or the like can be employed. BYZ has high proton conductivity at low operating temperatures and low activation energy, so it can increase energy efficiency. Moreover, since water which is a reaction product is generated on the outer side (second electrode layer side), the ammonia gas that is allowed to act on the inner side (first electrode layer side) is diluted with water vapor, thereby reducing the reaction efficiency. Can be prevented. Moreover, it is preferable that the gas decomposition apparatus is configured by combining a plurality of gas decomposition elements configured to include a solid electrolyte corresponding to each gas component.

One of the first electrode layer and the second electrode layer functions as a fuel-side anode electrode, and the other electrode layer functions as a cathode electrode. As long as the electrode layer can be provided with a catalyst having a required concentration and composition according to the type and concentration of the gas component, the material constituting the electrode layer is not particularly limited . When employing flop proton conductive solid electrolyte layer, the anode electrode, and the metal particles hormogone as a catalyst having an oxidation layer which is surface-oxidized, a main component and a proton conductive ceramic (BYZ, BCY, etc.) It can form from the sintered compact. For example, the anode electrode can be configured to include Fe and Ni catalyst components. On the other hand, the cathode electrode may Ni, Co, Ti, Mo, W, Mn, be configured to include at least one catalyst component selected Ru, from Cu.

  In the present invention, the composition of the metal particle chain as a catalyst is made different in a plurality of gas decomposing elements constituting the gas decomposing apparatus, and gas is sequentially acted on these gas decomposing elements to be decomposed.

When a gas decomposition apparatus is configured by arranging a plurality of gas decomposition elements in series, the concentration and composition of the catalyst in each gas decomposition element are set so that the maximum decomposition efficiency can be exhibited according to changes in the gas composition. Is preferred. For example, regarding the blending ratio of the first catalyst component and the second catalyst component of the catalyst in the plurality of gas decomposition elements, the one that causes the ammonia gas to act first is the one that causes the gas containing ammonia to act later. In comparison, it can be set so that the blending ratio of the first catalyst component is high and the blending ratio of the second catalyst component is low. The change in the mixing ratio of the catalyst in each gas decomposition element is set so that the gas can be decomposed most efficiently in accordance with the change in gas concentration and composition in the decomposition process. For example, similarly to the change of the catalyst component in the plurality of gas decomposition elements, each of the plurality of gas decomposition elements includes the first electrode of the gas in which the mixing ratio of the first catalyst component in the catalyst includes the ammonia. It can be configured such that the ratio of the second catalyst component in the catalyst decreases in the direction of flow in the bed and increases in the direction of flow of the gas containing ammonia in the first electrode layer.

In each gas decomposition element, the catalyst for varying the blending ratio is not limited to Fe as the first catalyst component and Ni as the second catalyst component, and other catalyst components can be added. .

On SL catalyst, and configured to include a Ni a Fe a second catalyst component is a first catalyst component, the mixing ratio of the first catalyst component and said second catalyst component, the flow of gas The gas decomposition apparatus can be configured by arranging the gas decomposition elements so as to change stepwise in the direction. For example, the first catalyst component is provided so that the blending ratio decreases stepwise in the gas flow direction, while the second catalyst component is blended in a stepwise ratio in the gas flow direction. It can be provided so as to increase.

When disassembling the ammonia gas, the decomposition initial, ammonia is decomposed into nitrogen molecules and hydrogen molecules. Thereafter, the hydrogen molecules are decomposed into protons and combined with oxygen at the anode or cathode electrode to produce water. In such a case, a mixed gas of ammonia gas and hydrogen gas is allowed to act on the anode electrode. Further, the concentration and composition of the mixed gas change in the process of gas decomposition. That is, the component ratio of ammonia gas is large at the beginning of the gas decomposition process, and the component ratio of hydrogen gas is large at the final stage of the gas decomposition process. Therefore, it is preferable to change the compounding ratio of the catalyst stepwise in the arranged gas decomposition elements in accordance with the change in the components of the mixed gas.

  When decomposing ammonia gas, it is preferable to employ a catalyst made of a Ni-Fe alloy. The Ni catalyst has high efficiency for decomposing hydrogen molecules. On the other hand, the Fe catalyst has high efficiency for decomposing ammonia gas. Therefore, it is preferable that the gas decomposition apparatus is configured so as to generate hydrogen molecules by promoting decomposition of ammonia gas at the initial stage of flow. For this reason, it is preferable that the composition ratio of the Fe catalyst is set to the maximum in the gas decomposition element arranged first, and is decreased stepwise in the gas flow direction. On the other hand, since hydrogen is finally combined with oxygen to produce water, the mixing ratio of the Ni catalyst is set to the minimum in the gas decomposition element arranged first, and the gas flow It is preferable to configure so as to increase stepwise in the direction.

In addition, a gas decomposition apparatus can be comprised including the several gas decomposition element in which the kind of catalyst was varied. For example, when decomposing a gas composed of a plurality of gas components, it is possible to configure a gas decomposing apparatus in which gas decomposing elements employing catalysts suitable for these gases are arranged at predetermined positions. When the first gas component may damage the electrolyte layer or electrode layer for decomposing the second gas component, the gas decomposing element for decomposing the first gas component is used as the second gas component. It can be placed in front of the gas decomposition element to be decomposed. Moreover, when it is necessary to decompose | disassemble gas with high precision, the gas decomposition | disassembly element provided with the catalyst component which can exhibit high decomposition efficiency also to low concentration gas can be arrange | positioned in the last stage of a gas decomposition process.

In addition, when a very toxic gas is removed, a single catalyst may not be able to cope with it. In the present invention, such a toxic gas, can also be configured by adding a gas decomposition device had use a plurality of types of catalysts.

In each gas decomposition element, there is no particular limitation on the part where the catalyst having a different blending ratio is provided. On SL catalyst can be formulated in the material constituting the electrode layer.

Further, provided with the catalyst layer on the surface of the upper Symbol solid electrolyte layer and / or electrode layer, it can be provided with different mixing ratio of the catalyst in the catalyst layer.

Moreover , while adding a catalyst to the electrical power collector provided adjacently along the said electrode layer, the compounding ratio of the said catalyst can also be varied.

The gas decomposition apparatus for decomposing a gas containing ammonia gas is the electrode where the gas is allowed to act, the catalyst comprising a first catalyst component and the second catalyst component are provided. As the first catalyst component is Fe is a catalyst component for producing hydrogen molecules are employed primarily decomposed ammonia gas. On the other hand, as the second catalyst component, Ni is a catalyst component for generating protons is employed to decompose the hydrogen molecule primarily.

In the case of decomposing a gas containing ammonia gas, the first catalyst includes at least one catalyst component selected from Fe, Co, Ti, Mo, W, Mn, Ru, and Cu. As the second catalyst, at least one catalyst component selected from Ni , Co, Ti, Mo, W, Mn, Ru, and Cu can be included.

The present invention can be applied to a gas decomposition apparatus that decomposes ammonia gas and a gas containing a plurality of other gas components.

The gas decomposition method according to the present invention is used for decomposition of a gas containing ammonia gas, which is performed using the gas decomposition apparatus described above. In the gas decomposition method, decomposition is performed by sequentially applying the gas to a plurality of gas decomposition elements having different compositions of the catalyst included in the first electrode layer .

In addition, as said gas , what contains gas components other than ammonia gas can also be decomposed | disassembled.

From a gas decomposition apparatus according to the present gun invention, it is possible to construct a gas decomposition generator.

  A catalyst according to the gas component that changes in the decomposition process can be made to act, and the efficiency of gas decomposition can be increased.

It is sectional drawing which shows schematic structure of the gas decomposition element which concerns on this invention. FIG. 2 is an enlarged cross-sectional view of a main part of the gas decomposition element shown in FIG. It is sectional drawing which follows the IB-IB line | wire in FIG. It is an expanded sectional view explaining the effect | action of the gas decomposition element which concerns on this invention. It is a figure which shows schematic structure of the gas decomposition apparatus comprised including a some gas decomposition element. It is a principal part expanded sectional view of the 1st gas decomposition element in the gas decomposition apparatus which concerns on 1st Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component. It is a principal part expanded sectional view of the 2nd gas decomposition element in the gas decomposition apparatus which concerns on 1st Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component. It is a principal part expanded sectional view of the 3rd gas decomposition element in the gas decomposition apparatus which concerns on 1st Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component. It is a principal part expanded sectional view of the 1st gas decomposition element in the gas decomposition apparatus which concerns on 2nd Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component. It is a principal part expanded sectional view of the 2nd gas decomposition element in the gas decomposition apparatus which concerns on 2nd Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component. It is a principal part expanded sectional view of the 3rd gas decomposition element in the gas decomposition apparatus which concerns on 2nd Embodiment, and is a figure which shows typically the mixture ratio of a catalyst component.

  Embodiments of the present invention will be specifically described below with reference to the drawings.

  As shown in FIG. 5, the gas decomposition apparatus 100 according to the present embodiment includes a plurality of gas decomposition elements 100a, 100b, and 100c. FIG. 1 is a cross-sectional view showing an outline of the gas decomposition element 100a (100b, 100c). In the present embodiment, the present invention is applied to a gas decomposition apparatus 100 that generates power by decomposing a gas containing ammonia gas.

Each gas decomposition element 100a (100b, 100c) includes a degrade cylindrical MEA 110a by flowing the gas inside (110b, 110c), said tubular MEA110 a (110b, 110c) the cylindrical holds the A cylindrical container 109 capable of allowing air to flow on the outer periphery of the MEA is configured.

Each cylindrical MEA 110a (110b, 110c) is held in the cylindrical container 109 so as to be connected between the gas inlet 107 and the gas outlet 108 of the cylindrical container 109. The outer periphery of the cylindrical container 109 is provided with an air inlet 117 for introducing air and an outlet 118 for discharging air flowing through the outer periphery of the cylindrical MEA 110 and generated moisture.

Each of the gas decomposition elements 100a (100b, 100c) is provided with a heater ( not shown ) on the outer periphery so that the cylindrical MEA 110a (110b, 110c) and the space S in which the air flows can be heated to a predetermined temperature. It is configured. Further, between the first electrode layer (anode electrode) 102a (102b, 102c) and the second electrode layer 105a (105b, 105c) (cathode electrode) of the cylindrical MEA 110a (110b, 110c) 111e and 112e are provided, and power storage means 500a (500b and 500c) is provided in the wiring.

  2 is an enlarged cross-sectional view of a main part of the gas decomposition apparatus 100, and FIG. 3 is a cross-sectional view taken along line IB-IB in FIG.

Each cylindrical MEA 110a (110b, 110c) includes a cylindrical solid electrolyte layer 101 and a first electrode layer (anode electrode) 102a (102b, 102c ) formed so as to cover the inner surface of the solid electrolyte layer 101. ) And a second electrode layer (cathode electrode) 105a (105b, 105c) formed to cover the outer surface of the solid electrolyte layer 101. Current collectors 111 and 112 are provided on the first electrode layer 102a (102b and 102c) and the second electrode layer 105a (105b and 105c) . The first electrode layer 102 is called a fuel electrode, and the second electrode layer 105 is called an air electrode. In the present embodiment, the cylindrical MEA 110a (110b, 110c) is employed, but the present invention is not limited to this, and the gas decomposition apparatus can be configured by combining MEAs including a flat solid electrolyte layer. Moreover, a dimension etc. can be set according to the apparatus to apply.

  The anode current collector 111 includes a silver paste coating layer 111g, a Ni mesh sheet 111a, a porous metal body 111s, and a central conductive rod 111k. The Ni mesh sheet 111a is configured to contact the first electrode layer 102 on the inner surface side of the cylindrical MEA 110 via the silver paste coating layer 111g and conduct from the porous metal body 111s to the central conductive rod 111k. Has been. For the porous metal body 111s, it is preferable to use a metal plated body capable of increasing the porosity, for example, Celmet (registered trademark: Sumitomo Electric Industries, Ltd.) in order to reduce the pressure loss of the gas containing ammonia. In order to reduce the electrical resistance between the first electrode layer 102 and the anode current collector 111, the silver paste coating layer 111g and the Ni mesh sheet 111a are disposed.

  The cathode side current collector 112 includes a silver paste coated wiring 112g and a Ni mesh sheet 112a. In the present embodiment, the Ni mesh sheet 112a is in contact with the outer surface of the cylindrical MEA 110 and is conducted to the external wiring. The silver paste coated wiring 112g contains silver that acts as a catalyst that promotes the decomposition of the oxygen gas in the second electrode layer (cathode electrode) 105 into oxygen ions, and lowers the electrical resistance of the cathode-side current collector 112. Contributes to The silver paste coated wiring 112g having a predetermined property is such that the silver particles come into contact with the second electrode layer (cathode electrode) 105 while passing oxygen molecules, and the silver particles contained in the second electrode layer (cathode electrode) 105 Equivalent catalytic action.

FIG. 4 is a diagram schematically showing the function of the main part when a proton conductive solid electrolyte is employed for the solid electrolyte layer 101. The gas containing ammonia is introduced from the gas inlet 107 into the inner cylinder of the cylindrical MEA 110 with strict airtightness, that is, the space where the anode current collector 111 is disposed. When the cylindrical MEA 110 is used, a porous metal body 111s is used because a gas containing ammonia is passed through the inner surface side. From the viewpoint of reducing the pressure loss, as described above, the porous metal plated body, for example, the above-mentioned Celmet can be used as the porous metal body 111s. The gas containing ammonia is partly decomposed into nitrogen gas and hydrogen gas as it passes through the voids of the porous metal body 111s, the Ni mesh sheet 111a, and the porous silver paste coating layer 111g. The
(Reaction at the anode side current collector): 2NH ₃ → N ₂ + 3H ₂

The ammonia passes through the current collector 111 and comes into contact with the first electrode layer 102, and undergoes the following ammonia decomposition reaction in the first electrode layer 102.
(Anode reaction): 2NH ₃ → N ₂ + 6H ⁺ + 6e ⁻
Further, the hydrogen gas generated by thermal decomposition when the ammonia passes through the anode-side current collector 111 is also decomposed into protons in the first electrode layer 102.
(Anode reaction): H ₂ → 2H ⁺ + 2e ⁻
The proton moves in the solid electrolyte layer 101 toward the second electrode layer 105. On the other hand, N ₂ is discharged from the gas outlet 108 as exhaust gas.

  That is, when the proton conductive solid electrolyte layer 101 is used, ammonia is decomposed into protons, nitrogen gas, and electrons in the first electrode layer 102. The generated protons move in the solid electrolyte layer 101 toward the second electrode layer 105. Since protons are smaller than oxygen ions, the moving speed in the solid electrolyte layer 101 is high, and the heating temperature of the apparatus can be set low.

On the other hand, in the second electrode layer 105, the protons that have moved through the solid electrolyte layer 101 react with oxygen in the air to generate water.
(Cathode reaction): 4H ⁺ + O ² + + 4e ⁻ → 2H ₂ O

  As a result of the above electrochemical reaction, electric power is generated, a potential difference is generated between the first electrode layer 102 and the second electrode layer 105, and current flows from the cathode side current collector 112 to the anode side current collector 111. I flows. By connecting the storage battery 500 between the cathode side current collector 112 and the anode side current collector 111, electric power is stored. Moreover, if it connects with a load, for example, the heater (not shown) for heating this gas decomposition element 100a instead of a storage battery, the electric power for it can be supplied.

  When an oxygen ion conductive solid electrolyte is employed, the reaction is to generate water inside the tubular MEA 110 (on the anode electrode side). Water may form water droplets at the low temperature near the outlet of the cylindrical MEA 110 and cause pressure loss. In contrast, when a proton conductive solid electrolyte is used as in this embodiment, protons, oxygen molecules, and electrons react on the outside (cathode side) to generate water. Since the outside is almost open, pressure loss is unlikely to occur even if water droplets adhere on the outlet side at low temperature.

<Solid electrolyte layer>
The solid electrolyte layer 101 is preferably formed of BYZ (yttrium-added barium zirconate). BYZ has high proton conductivity at low operating temperatures and low activation energy, so it can increase energy efficiency. In addition, with the above configuration, water as a reaction product is generated on the outside (second electrode layer side), so the ammonia gas that acts on the inside (first electrode 2 side) is diluted with water vapor and reacted. It is possible to prevent the efficiency from decreasing. Note that BCY (barium selete) may be used instead of the BYZ.

<First electrode layer (anode electrode)>
The first electrode layer 102 according to the present embodiment can be formed from a sintered body having an oxide layer on the surface and containing a metal particle chain functioning as a catalyst and ion conductive ceramics. In the present embodiment, proton conductive ceramics are employed as the ion conductive ceramics. For example, BYZ (yttrium-added barium zirconate) or BCY (barium selenate) can be employed. In the case of decomposing ammonia, it is preferable to employ one containing Ni and Fe as the metal of the metal particle chain. Moreover, what contains Ni-Co, Co-Fe, Ni-Ru, Ni-W, etc. is employable.

<Second electrode layer (cathode electrode)>
The second electrode layer 105 (cathode electrode) can be formed using a ceramic sintered body having proton conductivity in the same manner as the material constituting the first electrode layer 102 (anode electrode). In addition, a catalyst such as silver can be added to promote the reaction between protons and oxygen. Also, depending on the type of gas to be decomposed, a metal particle chain can be blended similarly to the first electrode layer 102 described above. The second electrode layer 105 (cathode electrode) can also be formed in the same manner as the first electrode layer 102 (anode electrode).

  As described above, in the present embodiment, a mixed gas of ammonia gas and hydrogen gas is allowed to act on the first electrode layer 102 to be decomposed as described above. The metal particle chain blended as the catalyst is formed from a Ni-Fe alloy suitable for decomposing the mixed gas, but Fe has a high ammonia gas decomposing efficiency, while Ni is a decomposing hydrogen gas. High efficiency.

  The ammonia gas is decomposed while flowing in the axial direction inside the cylindrical MEA. For this reason, the concentration of the mixed gas composed of ammonia gas and hydrogen gas is the highest near the gas inlet of the cylindrical container, decreases as it flows in the cylindrical MEA in the axial direction, and becomes the lowest near the gas outlet. . The ammonia gas decreases from the gas inlet to the gas outlet because the decomposition reaction in the current collector and the decomposition reaction in the first electrode layer 102 (anode electrode) proceed simultaneously. On the other hand, since there is a certain time difference until the hydrogen gas is decomposed after the ammonia gas is decomposed in the current collector, the decrease in the concentration of hydrogen gas is smaller than the decrease in the concentration of ammonia gas. As a result, at the initial stage of gas flow, the component ratio of ammonia gas is larger than the component ratio of hydrogen gas, but the ratio of hydrogen gas increases as it flows, and in the vicinity of the gas outlet, no decomposition occurs. Most of the gas will be hydrogen gas. Since the first electrode layer 102 in the conventional gas decomposition element is configured by blending a catalyst having a uniform composition, it cannot cope with the change in the concentration of the ammonia gas, and the decomposition performance cannot be improved.

  In the present embodiment, as shown in FIG. 5, the gas decomposition elements 100a, 100b, and 100c having different catalyst blending ratios in stages corresponding to changes in the gas concentration and the component ratio are used. The gas decomposition apparatus 100 is comprised.

  6 to 8 schematically show the difference in the mixing ratio of the catalyst in each of the gas decomposition elements 100a, 100b, and 100c. In the present embodiment, the composition of the catalyst of the first electrode layer 102 (anode electrode) in each gas decomposition element is different. As shown in these drawings, the mixing ratio of the Fe catalyst 151 in the first electrode layer 102a (anode electrode) of the gas decomposition element 100a through which gas is first passed is set to be the largest, and the second gas decomposition element 100b. The blending ratio of the Fe catalyst 151 in the third gas decomposition element 100c is decreased stepwise. On the other hand, the mixing ratio of the Ni catalyst 152 is set to be the smallest in the first electrode layer (anode electrode) 102a of the gas decomposition element 100a through which gas is first passed. The blending ratio in 100b and the third gas decomposition element 100c is increased stepwise.

  By adopting the above-described configuration, it is possible to promote the decomposition of ammonia gas at the initial stage of gas decomposition, and to enhance the decomposition ability of hydrogen gas whose component ratio increases as it flows. Thereby, it is possible to efficiently decompose the gas whose concentration and component ratio change while flowing in the plurality of cylindrical MEAs.

  There is no particular limitation on the method of forming the first electrode layer 102 having a different catalyst mixing ratio. For example, when the solid electrolyte layer and the electrode layer are integrally formed by a sintering technique, the blending ratio of the catalyst in the electrode layer can be varied in the molding process. The mixing ratio of the Ni—Fe in each gas decomposition element is not particularly limited. For example, the mixing ratio of Ni—Fe in the first gas decomposition element 100a is 1: 9, the mixing ratio of Ni—Fe in the second gas decomposition element 100b is 5: 5, and the third gas decomposition element 100c The blending ratio of Ni—Fe can be 9: 1.

  In the embodiment shown in FIGS. 6 to 8, the mixing ratio of the catalyst in the second electrode layers 105 a, 105 b, and 105 c is not changed, but depending on the type of gas to be decomposed and the configuration of the apparatus, The blending ratio can be changed.

  In the first embodiment, the anode current collector 111 is provided with a catalyst made of silver paste, but can be replaced with a catalyst made of Ni—Fe. The mesh sheet made of Ni-Fe is, for example, a composite catalyst mesh sheet having a different Ni-Fe component blending ratio by providing a Ni plating layer with different thickness on the Fe mesh sheet and heating it to alloy. Can be formed.

  9 to 11 show a second embodiment of the present invention. In the second embodiment, a gas decomposition apparatus 200 is configured by combining a plurality of gas decomposition elements 200a, 200b, and 200c having different catalysts. 9 to 11 are diagrams schematically showing the main part of each gas decomposition element in FIG. 5, and correspond to FIGS. 6 to 8 according to the first embodiment. In addition, since the configuration other than the solid electrolyte layer and the first electrode layer is the same as that of the first embodiment, the description thereof is omitted.

  As described above, the Ni—Fe catalyst is effective for decomposing ammonia gas. On the other hand, the Ni-Fe catalyst is not effective for all gases. In the present embodiment, the present invention is applied to a gas decomposition apparatus 200 that can be applied to a mixed gas containing ammonia gas and methane gas.

  In the present embodiment, the first gas decomposition element 200a capable of effectively decomposing methane gas, the second gas decomposition element 200b capable of effectively decomposing ammonia gas, and the gas decomposition element 200b disposed in front mainly. A gas decomposition apparatus 200 shown in FIG. 5 is configured by connecting in series with a third gas decomposition element 200c capable of effectively decomposing hydrogen. The gas decomposition apparatus 200 according to the present embodiment is configured to include one gas decomposition element having a catalyst having a different composition as described above. In each of the gas decomposition elements 200a, 200b, and 200c, a catalyst composition is provided. A plurality of gas decomposition elements having different ratios can be provided.

  A first gas decomposition element 200a including the first cylindrical MEA 210a shown in FIG. 9 includes a solid electrolyte layer 201a having oxygen ion conductivity such as YSZ and includes a catalyst made of Ru—Ni. 202a (anode electrode) is employed.

In the first gas decomposition element 200a, the mixing ratio of the Ru catalyst 252 is set higher than that of the Ni catalyst 251 in order to increase the decomposition efficiency of methane gas. For example, it is preferable to set the blending ratio of Ru—Ni to 7: 3 or more. With the above configuration, the first gas decomposition element 200a is configured so as to be able to efficiently decompose mainly methane gas out of the mixed gas components. The reaction in the first electrode layer 202a (anode electrode) in the first gas decomposition element 200a is as follows.
(Anode electrode reaction): CH ₄ + 4O ²⁻ → 2H ₂ O + CO ₂ + 8e ⁻
The water vapor 2H ₂ O and carbon dioxide gas CO ₂ generated by the anode reaction in the first electrode layer 202a are discharged to the atmosphere after passing through another gas decomposition element.
Incidentally, by providing a current collector having a catalyst, it can also be applied to the first electrode layer from causing a reaction for generating hydrogen.

In the second electrode layer 205a (cathode electrode), oxygen ions O ²⁻ used in the anode reaction are generated from the air and moved in the solid electrolyte layer 201a toward the first electrode layer 202a (anode electrode). It is done.
(Cathode reaction): 2O ₂ + 8e ⁻ → 4O ²⁻
By adopting the above configuration, methane gas can be mainly decomposed efficiently in the first gas decomposition element 200a.

Further, when the gas decomposition element is formed using a proton conductive solid electrolyte such as BYZ, in the first electrode layer,
(Anode reaction)
CH ₄ → C + 2H ₂
2H ₂ → 4H ⁺ + 4e ^-
Occurs.
Hydrogen ions generated by the anode reaction are moved in the solid electrolyte layer to the second electrode layer. In the second electrode layer,
(Cathode reaction)
4H ⁺ + O2 + 4e ⁻ → 2H ₂ O
The water vapor generated by the cathode reaction is released to the atmosphere.

  Similar to the first embodiment, the second gas decomposition element 200b including the second cylindrical MEA 210b shown in FIG. 10 is provided for decomposing ammonia gas, and is the same as in the first embodiment. In addition, the first electrode layer 202b (anode electrode) containing a catalyst made of Fe—Ni is employed. In order to efficiently decompose the ammonia gas, the blending ratio of the Fe catalyst 251 is set higher than the blending ratio of the Ni catalyst 253. In the present embodiment, it is preferable to set the Fe—Ni blending ratio to 7: 3 or more.

  In the second gas decomposition element 200b, ammonia gas is decomposed in the same manner as in the first embodiment described above. In addition, since the blending ratio of Fe—Ni is set to 7: 3 or more, the hydrogen gas cannot be sufficiently decomposed. For this reason, in order to decompose | disassemble hydrogen gas efficiently, the 3rd gas decomposition | disassembly element 200c shown in FIG. 11 is provided.

  In the first electrode layer 202c of the third gas decomposition element 200c, the Fe—Ni blending ratio is set to 9: 1. By adopting the above configuration, the hydrogen gas that could not be decomposed by the first gas decomposition element 200a and the second gas decomposition element 200b can be efficiently decomposed.

  By adopting the above configuration, it is possible to efficiently decompose the mixed gas containing methane gas and ammonia gas.

  In the above-described embodiment, the gas decomposition element according to the present invention is applied to the decomposition of the mixed gas containing ammonia gas and methane gas, but the present invention can also be applied to a gas decomposition apparatus that decomposes other gases.

  The scope of the present invention is not limited to the embodiment described above. The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not by the above-mentioned meaning but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  A gas whose concentration or composition changes while flowing can be efficiently decomposed and removed, and power can be generated efficiently using a decomposition reaction.

DESCRIPTION OF SYMBOLS 100 Gas decomposition apparatus 100a 1st gas decomposition element 100b 2nd gas decomposition element 100c 3rd gas decomposition element 110a 1st cylindrical MEA
110b Second cylindrical MEA
110c Third cylindrical MEA
102a First electrode layer (anode electrode)
102b First electrode layer (anode electrode)
102c 1st electrode layer (anode electrode)
105a Second electrode layer (cathode electrode)
105b Second electrode layer (cathode electrode)
105c Second electrode layer (cathode electrode)

Claims (4)

A solid electrolyte layer;
A first electrode layer provided on one side of the solid electrolyte layer;
A second electrode layer provided on the other side of the solid electrolyte layer;
A plurality of gas decomposition elements comprising: a catalyst containing Fe as the first catalyst component and Ni as the second catalyst component;
A gas decomposition apparatus that decomposes a gas containing ammonia by sequentially causing a gas containing ammonia to act on the plurality of gas decomposition elements,
In each of the plurality of gas decomposition elements, the gas containing ammonia is decomposed into nitrogen and hydrogen in the first electrode layer, the hydrogen is further decomposed into protons, and the protons pass through the solid electrolyte layer. The second electrode layer reacts with the protons and oxygen to produce water,
The catalyst is
It is mix | blended in the material which comprises the said 1st electrode layer, is mix | blended in the catalyst layer provided in the surface of the said 1st electrode layer, or adjoins along the said 1st electrode layer. Or is added to the current collector provided in the first electrode layer,
Regarding the mixing ratio of the first catalyst component and the second catalyst component of the catalyst in the plurality of gas decomposition elements, the one that causes the ammonia gas to act first is compared to the one that causes the gas containing ammonia to act later. A gas decomposition apparatus in which the blending ratio of the first catalyst component is high and the blending ratio of the second catalyst component is low. A method for decomposing a gas containing ammonia gas, which is performed using the gas decomposing apparatus according to claim 1 ,
A gas decomposition method, in which the gas is sequentially applied to a plurality of gas decomposition elements having different compositions of the catalyst contained in the first electrode layer for decomposition. The gas decomposition method according to claim 2 , wherein the gas includes a plurality of gas components. A gas decomposition power generation apparatus comprising the gas decomposition apparatus according to claim 1.

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