JP2012157848A - Gas decomposing apparatus, power generator, and method of decomposing gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas decomposing apparatus and a method of decomposing a gas, capable of enhancing decomposition efficiency by increasing the temperature of a cylindrical MEA (Membrane Electrode Assembly) and a gas to be subjected to decomposition, and of reducing the electric power necessary for the heating.SOLUTION: The gas decomposing apparatus 100 constituted of a cylindrical MEA (Membrane Electrode Assembly) 7 including a cylindrical solid electrolyte layer 1, a first electrode layer 2 formed and overlaid on the inner circumference thereof, and a second electrode layer 5 formed and overlaid on the outer circumference thereof, has a heating container 51 that houses and heats the cylindrical MEA, and further includes an auxiliary heating device 71 capable of firing a combustible gas present in exhaust generated by a gas decomposition reaction to auxiliarily heat the heating container.

Description

  The present invention relates to a gas decomposition apparatus, a power generation apparatus, and a gas decomposition method. Specifically, the present invention relates to a gas decomposition apparatus capable of efficiently decomposing a predetermined gas, a power generation apparatus including the gas decomposition apparatus, and a gas decomposition method.

  For example, ammonia is an indispensable compound for agriculture and industry, but is harmful to humans, so various methods for decomposing ammonia in water and air are known. In order to decompose and remove ammonia from water containing a high concentration of ammonia, a method has been proposed in which ammonia water is sprayed and contacted with an air stream to separate ammonia in the air and contacted with hypobromous acid solution or sulfuric acid. (Patent Document 1). In addition, a method of separating ammonia in the air by the same process as the above method and burning it with a catalyst (Patent Document 2) and a method of decomposing ammonia-containing wastewater into nitrogen and water using a catalyst have been proposed. (Patent Document 3). Furthermore, the waste gas of the semiconductor manufacturing apparatus often contains ammonia, hydrogen, etc., and in order to completely remove the odor of ammonia, it is necessary to remove it to the ppm order. For this purpose, many methods have been used in which harmful gas is absorbed in water containing chemicals through a scrubber when the waste gas of the semiconductor device is released. On the other hand, in order to decompose harmful gases at a low running cost without input of energy, chemicals, etc., a waste gas treatment method in a semiconductor manufacturing apparatus or the like that decomposes ammonia with a phosphoric acid fuel cell has been proposed (patent) Reference 4).

JP-A-7-31966 Japanese Patent Laid-Open No. 7-116650 Japanese Patent Laid-Open No. 11-347535 JP 2003-45472 A Japanese Patent No. 3238086

  A method using a chemical such as a neutralizing agent as described in Patent Document 1, a method of burning as described in Patent Document 2, and a thermal decomposition using a catalyst as described in Patent Document 3 Ammonia can be decomposed by a reaction method. However, these methods require chemicals and external energy (fuel), and further require periodic replacement of the catalyst, resulting in increased running costs.

  In addition, since the apparatus becomes large, it is difficult to secure a space when it is additionally provided in existing facilities. In addition, for the device that uses phosphoric acid fuel cells to remove ammonia in the exhaust gas from the production of compound semiconductors, the electrolyte is liquid, so the partition between the air side and the ammonia side cannot be made compact, and the size of the device is reduced. There was a problem that was difficult.

  In order to solve the above problem, as described in Patent Document 5, a cylindrical solid electrolyte layer, and a first electrode layer and a second electrode layer formed so as to sandwich the solid electrolyte layer from inside and outside A cylindrical MEA (Membrane Electrode Assembly) configured with the above can be employed. A gas containing a gas to be decomposed is caused to flow in the axial direction in the inner space of the cylindrical MEA.

  In order to decompose the gas, it is preferable that the temperature of the gas containing the gas is increased as much as possible to act on the first electrode layer (fuel electrode) of the cylindrical MEA. For this reason, the cylindrical MEA is accommodated in a heating container, and the heating container is heated by a heater to heat the cylindrical MEA and the gas acting on the cylindrical MEA.

  In order to perform the gas decomposition reaction efficiently, the temperature in the heating container must be maintained at 800 to 850 ° C. For this reason, the power consumption of the heater is increased.

  This invention makes it a subject to provide the gas decomposition apparatus and gas decomposition method which can reduce the electric power for heating the said heating container.

  The invention described in claim 1 of the present application is formed by stacking a cylindrical solid electrolyte layer, a first electrode layer formed on the inner periphery of the solid electrolyte layer, and an outer periphery of the solid electrolyte layer. A gas decomposition apparatus configured using a tubular MEA (Membrane Electrode Assembly) having a second electrode layer, and including a heating container that accommodates and heats the tubular MEA, An auxiliary heating device is provided that can burn the combustible gas in the generated exhaust gas to auxiliary heat the heating vessel.

When gas is decomposed using a cylindrical MEA, combustible gas may be contained in the exhaust gas. For example, when ammonia gas is decomposed using the cylindrical MEA, theoretically, ammonia is decomposed into nitrogen gas and water. Part is directly decomposed as 2NH ₃ → N ₂ + 3H ₂ . In addition, when decomposing a hydrocarbon-based gas such as methane, carbon monoxide, carbon dioxide, and the like are generated, so these gases can also be applied.

  That is, combustible hydrogen gas is generated in the heated flow path. The hydrogen gas is directly discharged as exhaust gas. In the present invention, combustible gas such as hydrogen gas is recycled and burned by the auxiliary heating device, and the generated heat is applied to the heating container for auxiliary heating. Thereby, the power consumption of the heater which heats the said heating container can be reduced.

  The means for burning the combustible gas is not particularly limited. For example, as in the invention described in claim 2, the auxiliary heating device can be configured to include a burner capable of heating the heating container by burning the combustible gas. By burning the combustible gas with a burner and adding combustion heat to the heating vessel, the power consumption of the heater for heating the heating vessel can be reduced.

  Further, as in the invention described in claim 3, the auxiliary heating device can be configured to include a catalytic combustion device that combusts the combustible gas by a catalytic reaction.

  By utilizing a catalytic reaction, gas can be burned even when the concentration of combustible gas is low. For example, the generated combustible gas can be burned by using platinum, palladium, nickel or the like as a combustion catalyst.

  In general, when gas is burned using a catalytic reaction, the higher the temperature, the higher the efficiency. According to a fourth aspect of the present invention, the combustible gas is combusted by applying the temperature of the heating container to the catalytic combustion apparatus.

  As described above, in the present invention, the heating container is heated to 800 ° C. or higher. For this reason, by making the temperature of the heating container act on the catalyst, it becomes possible to efficiently burn the combustible gas. The method for causing the temperature of the heating container to act on the catalyst is not particularly limited. For example, a catalytic combustion apparatus can be provided in contact with the heating container, or can be provided in the heating container.

  When combustible gas is combusted, the gas discharged from the gas decomposition apparatus can be directly supplied to a burner or a catalyst combustion apparatus constituting the preheating apparatus and combusted. Further, as in the invention described in claim 5, it is also possible to provide a gas separation device for separating the combustible gas from the exhaust gas, and to burn only the combustible gas. For example, when decomposing ammonia gas, exhaust gas containing hydrogen is discharged as a combustible gas. The exhaust gas contains nitrogen and water vapor, and its combustion efficiency is poor if it is directly burned by an auxiliary heating device. For this reason, it is preferable to provide a gas separator that can pour out hydrogen gas.

  The principle and configuration of the gas separation device are not particularly limited. For example, it can be configured using a filter or the like that can separate hydrogen gas, which is a combustible gas, from other gas components. It can also be separated using an adsorbent such as activated carbon or zeolite.

Further, there may be a case where harmful gas is generated by burning. In such a case, an additive gas that can be combusted without generating the harmful gas may be added and combusted. For example, when harmful NO _X is generated, it can be rendered harmless by adding ammonia gas or methane-based gas and burning it.

  The invention described in claim 6 is the application of the present invention when the gas to be decomposed is a gas containing ammonia and the combustible gas to be generated is hydrogen. Details of the application to ammonia gas will be described later.

  The form of the cylindrical MEA is not particularly limited. Cylindrical MEAs configured to have open end portions at both ends, provide protrusions at the open end portions, connect connection members, and cause gas to flow in one direction can be employed.

  In addition, the cylindrical MEA is provided with a lower end sealed, and is inserted into a sealing portion disposed in the heating container and an internal space of the cylindrical MEA. A gas induction pipe that forms a cylindrical flow channel with the peripheral surface is provided, and the gas introduced into the gas induction pipe through the connection member provided at the upper end is directed toward the sealing portion. The first electrode layer is made to flow and reversely flow by flowing out from the inside of the induction pipe in the vicinity of the sealing portion, and the cylindrical flow path is made to flow in a direction opposite to the flow in the gas induction pipe. It can be configured to be decomposed by acting on and discharged through the connecting member.

  By adopting the above configuration, it is possible to provide a connection member for allowing gas to enter and exit only at the upper end, and it is sufficient to provide a sealing structure between the cylindrical MEA and the connection member in one place. Therefore, the reliability of connection is increased. In addition, the number of parts and processing steps can be reduced.

  In addition, by adopting the above configuration, the gas flowing through the cylindrical MEA can flow a distance twice as long as the cylindrical length of the cylindrical MEA. For this reason, after raising the temperature of gas in the said gas induction pipe, it can be made to act on the said cylindrical MEA. Therefore, it is possible to increase the gas decomposition efficiency, and it is possible to increase the gas throughput by increasing the gas flow rate.

  The materials constituting the first electrode layer and the second electrode layer are not particularly limited. For example, as in the invention described in claim 7, the first electrode layer and / or the second electrode layer is formed of a metal particle chain mainly composed of nickel (Ni), an ion conductive ceramic, It can be set as the sintered body containing this. The metal particle chain refers to a bead-like elongated metal body formed by connecting metal particles. Ni, Fe-containing Ni, or Ni, Fe-containing Ni may be a metal containing a small amount of Ti. In a state where Ni or the like is oxidized, the surface of the metal particle chain is oxidized, and the contents (portion inside the surface layer) are not oxidized and retain the conductivity of the metal.

For this reason, for example, when the ion moving in the solid electrolyte layer is an anion (in some cases, it is a cation), the following effects are produced.
(A1) When a metal particle chain is contained in the first electrode layer (anode), in the first electrode layer (anode), the anion moving from the solid electrolyte layer and the first electrode layer ( The chemical reaction with the gas molecules in the gas led from the outside of the anode) to the first electrode layer (anode) is promoted by the oxidation layer of the metal particle chain (catalysis), and an anion is added. The chemical reaction in the first electrode layer (anode) is promoted (acceleration effect by electric charge). And as a result of the chemical reaction, the conductivity of the generated electrons can be ensured by the metal portion of the metal particle chain. As a result, the electrochemical reaction involving charge transfer in the first electrode layer (anode) can be accelerated as a whole. When the metal particle chain is contained in the first electrode layer (anode), a cation, for example, a proton is generated in the first electrode layer (anode), and the second electrode layer (cathode) is generated in the solid electrolyte layer. The cation can be moved to the surface, and the above-mentioned promoting action by the charge can be obtained similarly.
However, the oxide layer of the metal particle chain is surely formed by firing before use, but the oxide layer is often lost due to a reduction reaction during use. Even if the oxide layer disappears, the above-described catalytic action may or may not be reduced. In particular, Ni containing Fe or Ti has high catalytic action even without an oxide layer.
(A2) When the second electrode layer (cathode) contains a metal particle chain in the second electrode layer (cathode), the second electrode layer (cathode) from the outside of the second electrode layer (cathode). The chemical reaction of gas molecules in the gas led to gas) is promoted by the oxidation layer of the metal particle chain (catalysis), and the conductivity of the electrons from the external circuit is improved and the electrons are allowed to participate. The chemical reaction at the second electrode layer (cathode) is promoted (acceleration effect by electric charge). Then, anions can be efficiently generated from the molecules and delivered to the solid electrolyte layer. As in (A1), in the case of (A2), the electrochemical reaction between the cation that has moved through the solid electrolyte layer, the electrons that have flowed through the external circuit, and the second gas can be promoted. For this reason, the electrochemical reaction accompanied by transfer of electric charge in the second electrode layer (cathode) can be accelerated as a whole, as in the case of being included in the first electrode layer (anode). In what case, the metal particle chain is included in the second electrode layer (cathode) depending on the gas to be decomposed.
(A3) When the metal particle chain is contained in the first electrode layer (anode) and the second electrode layer (cathode), the effects (A1) and (A2) can be obtained.

  In many cases, the electrochemical reaction is limited by the moving speed or moving time of the solid electrolyte layer of ions. In order to increase the moving speed of ions, the gas decomposing apparatus generally includes a heating device that can accommodate the entire cylindrical MEA, such as a heater, and is usually set to a high temperature, for example, 600 ° C to 1000 ° C. By raising the temperature, not only the ion transfer speed but also a chemical reaction accompanied by charge transfer in the electrode layer is promoted.

  When the ions moving through the solid electrolyte layer are anions, they are generated and supplied by a chemical reaction at the second electrode layer (cathode) as described above. Molecules in the fluid and electrons introduced in the second electrode layer (cathode) react to generate anions. The generated anion moves in the solid electrolyte layer to the first electrode layer (anode). The electrons participating in the reaction at the second electrode layer (cathode) include an external circuit (capacitor, power source, and power consuming device) that connects the first electrode layer (anode) and the second electrode layer (cathode). ) Comes in. When the ions moving through the solid electrolyte layer are cations, they are generated by an electrochemical reaction in the first electrode layer (anode) and move through the solid electrolyte layer to the second electrode layer (cathode). Electrons are generated at the first electrode layer (anode) and flow through an external circuit to the second electrode layer (cathode) to participate in the electrochemical reaction at the second electrode layer (cathode). The electrochemical reaction may be a power generation reaction as a fuel cell, or may be an electrolysis reaction.

  As in the invention described in claim 8, the solid electrolyte layer can be configured to have oxygen ion conductivity or proton conductivity. When an oxygen ion conductive solid electrolyte is used, for example, electrons and oxygen molecules are reacted in the second electrode layer (cathode) to generate oxygen ions, which are then moved in the solid electrolyte layer. A predetermined electrochemical reaction can be caused in one electrode layer (anode). In this case, since the moving speed of oxygen ions in the solid electrolyte layer is not large compared to protons, the temperature is sufficiently increased and / or the thickness of the solid electrolyte layer is sufficiently thin to obtain a practical level of decomposition capacity. Such measures are necessary.

On the other hand, barium zirconate (BaZrO ₃ ) is known as a proton conductive solid electrolyte. When a proton conductive solid electrolyte is used, for example, ammonia is decomposed at the first electrode layer (anode) to generate protons, nitrogen molecules and electrons, and this proton is passed through the solid electrolyte layer to the second electrode layer. It moves to (cathode) and reacts with oxygen in the second electrode layer (cathode) to produce water (H ₂ O). Since protons are small compared to oxygen ions, the moving speed in the solid electrolyte layer is high, and a practical decomposition capacity can be obtained by lowering the heating temperature.

  As in the ninth aspect of the invention, the power generation apparatus may be configured by using the gas to be decomposed as fuel and including the above-described gas decomposition apparatus according to the present invention.

  According to a tenth aspect of the present invention, there is provided a cylindrical solid electrolyte layer, a first electrode layer formed on the inner periphery of the solid electrolyte layer, and a first electrode layer formed on the outer periphery of the solid electrolyte layer. A gas decomposition method performed by a gas decomposition apparatus configured using a cylindrical MEA (Membrane Electrode Assembly) having two electrode layers, wherein the cylindrical MEA is heated in a heating vessel to decompose the gas In addition, combustible gas in the exhaust gas generated by the gas decomposition reaction is combusted to supplementally heat the heating container.

  Power consumption for heating the container can be reduced by auxiliary heating the heating container for heating the cylindrical MEA using the combustible gas generated in the gas decomposition reaction.

It is a figure which shows schematic structure of the gas decomposition apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows the structure in the heating container of the gas decomposition apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing which follows the III-III line in FIG. It is a figure which shows the electrical wiring system | strain of the gas decomposition apparatus of FIG. It is a longitudinal cross-sectional view by the side of the protrusion part (opening end side) of the gas decomposition apparatus shown in FIG. It is a figure which shows schematic structure of the gas decomposition apparatus which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a gas decomposition apparatus 100 according to a first embodiment of the present invention.

  In the first embodiment, a gas decomposition apparatus 100 is configured by housing a plurality of gas decomposition elements 10 each including a cylindrical MEA 7 in a heating container 51.

  The cylindrical MEA 7 is provided with a protruding portion 41 by accommodating the lower portion in the heating container 51 and causing the upper portion to protrude upward from the heating container. A connecting member 30 is provided at the opening end of the upper end of the cylindrical MEA 7, and a first gas containing a gas decomposed into the cylindrical MEA is introduced through the connecting member 30. The exhaust gas after decomposition is configured to be discharged.

  The heating container 51 is provided with a heater 52. By operating the heater 52, the cylindrical MEA 7 and the first and second gases that act on the cylindrical MEA 7 are heated. ing. The heater 52 is configured to be controlled by a control device (not shown), and is configured to be able to maintain a predetermined temperature in the heating container 51 at, for example, 800 to 1000 ° C.

  As will be described later, the exhaust gas discharged from the connection member 30 includes hydrogen gas. In the present embodiment, the exhaust pipe 65 extending from the connecting member is connected to the hydrogen separator 71, and hydrogen is separated in the hydrogen separator 71 and supplied to the gas burner 72 for combustion. Yes. The gas burner 72 is configured to heat the heating container 51, and is configured to reduce power consumption of the heater 52 that heats the heating container 51.

  FIG. 2 is a longitudinal sectional view showing the structure inside the heating container 51 in the gas decomposition apparatus 100. 3 is a cross-sectional view taken along line III-III in FIG. In the present embodiment, a gas decomposing apparatus in the case where the first gas used for decomposition is an ammonia-containing gas will be described.

The gas decomposition element 10 is provided with a first electrode layer (anode) 2 so as to cover the inner surface of the cylindrical solid electrolyte layer 1, and a second electrode layer (cathode) 5 so as to cover the outer surface. The cylindrical MEA 7 (1, 2, 5) is provided. The first electrode layer (anode) 2 may be called a fuel electrode, and the second electrode layer (cathode) 5 may be called an air electrode.
In the present embodiment, as described above, the ammonia-containing gas flows as the first gas inside the cylindrical MEA 7 (1, 2, 5). In addition, air, which is an oxygen-containing gas, flows as the second gas outside the cylindrical MEA 7 (1, 2, 5). The flow path inside the cylindrical MEA 7 (1, 2, 5) through which the first gas flows is defined as the first gas flow path 91 and the cylindrical MEA 7 (1, 2 through which the second gas flows). The space S in the heating container 51 outside 5) is used as the second gas flow path. The cylindrical MEA 7 (1, 2, 5) according to the present embodiment is formed in a right cylindrical shape as shown in FIG. The inner diameter of the cylindrical MEA 7 (1, 2, 5) is, for example, about 20 mm, but the dimensions and the like can be set according to the device to be applied.

  In the gas decomposing element 10 of the present embodiment, the cylindrical MEA 7 (1, 2, 5) is sealed at its lower end and a gas induction pipe 11k is inserted from the upper end. The gas induction pipe 11k is an alloy containing iron, chromium, niobium, molybdenum, etc. based on Ni such as stainless steel, copper, nickel, inconel, that is, heat resistance to 600 to 1000 ° C. and ammonia gas corrosion resistance. Consists of a material with The lower end portion is provided with a sealing portion 44 by extending the solid electrolyte layer 1 of the cylindrical MEA 7 (1, 2, 5) and the first electrode layer 2 located on the inner side and providing a bottom portion. ing.

  The gas induction pipe 11k is inserted from the upper end portion of the cylindrical MEA 7 (1, 2, 5) toward the sealing portion 44 that is the lower end portion, and the first electrode layer of the cylindrical MEA 7 is inserted. The cylindrical flow path 43 is set between the inner peripheral surface 2 and the outer peripheral surface of the gas guide pipe 11k. A porous metal body 11s is inserted into the cylindrical flow path 43, and the gas guide pipe 11k is held at the center while the outer peripheral surface of the gas guide pipe 11k and the first electrode layer 2 are in contact with each other. A cylindrical flow path 43 is formed between the inner peripheral surface.

  In the gas decomposition element 10 according to the present embodiment, the first gas is caused to flow toward the sealing portion 44 in the internal space 42 of the gas guiding pipe 11k, and the gas guiding pipe is disposed in the vicinity of the sealing portion 44. The first gas is allowed to flow out from the inside of 11k and reversed, and the first gas is caused to flow in the direction opposite to the flow in the internal space 42 through the cylindrical flow path 43. That is, the first gas flow path 91 is configured by the internal space 42 and the cylindrical flow path 43.

  By adopting the above configuration, the first gas flow path 91 can have a distance of about twice the cylinder length of the cylindrical MEA 7 in the space inside the cylindrical MEA 7. For this reason, it can be made to act on the said cylindrical MEA7 in the state heated enough in the said gas induction pipe 11k, and temperature rising. Therefore, the decomposition efficiency of the first gas can be increased, and the gas flow rate can be increased to increase the gas throughput.

  The gas induction pipe 11k is made of a conductive metal such as stainless steel, and is configured to function as a component of the anode current collector 11. On the other hand, the cathode current collector 12 is arranged so as to wrap around the outer surface of the second electrode layer (cathode) 5.

The anode current collector 11 includes a silver paste coating layer 11g, a Ni mesh sheet 11a, the porous metal body 11s, and the gas induction pipe 11k. The Ni mesh sheet 11a is in contact with the first electrode layer (anode) 2 on the inner surface side of the cylindrical MEA 7 through the silver paste coating layer 11g, and conducts from the porous metal body 11s to the gas induction pipe 11k. Is configured to do. By providing the silver paste coating layer 11g, the electrical resistance between the first electrode layer 2 and the anode current collector can be reduced. The tip portion W ₁ of the Ni mesh sheet 11a is in the vicinity of the sealing portion 44 is conductively connected to wind through the bonding member W ₂ band-like on an outer peripheral portion of the gas introduction pipe 11k . Therefore, the Ni mesh sheet 11a includes, in parallel, a conductive path of (1) Ni mesh sheet 11a / porous metal body 11s / gas induction pipe 11k, and (2) Ni mesh sheet 11a / gas induction pipe 11k, The conductive path is formed. As a result, it is possible to prevent an increase in pressure loss while being located on the inner surface of the cylindrical MEA 7 and maintaining a low electrical resistance.

  As the porous metal body 11s, in order to reduce the pressure loss of the first gas, it is preferable to use a metal plated body that can increase the porosity, such as Celmet (registered trademark: Sumitomo Electric Industries, Ltd.).

  The cathode current collector 12 includes a silver paste coated wiring 12g and a Ni mesh sheet 12a. In the present embodiment, the Ni mesh sheet 12a is in contact with the outer surface of the cylindrical MEA 7 and conducts to the external wiring 12e shown in FIG. The silver paste coated wiring 12g contains silver that acts as a catalyst for promoting the decomposition of oxygen in the oxygen-containing gas (air), which is the second gas, into oxygen ions in the second electrode layer (cathode) 5. In addition, this contributes to lowering the electrical resistance of the cathode current collector 12. The silver paste coated wiring 12g has a catalytic action equivalent to that of the silver particles contained in the second electrode layer (cathode) 5 by contacting the silver particles with the second electrode layer (cathode) 5 while passing oxygen molecules. To express.

  The space S in the heating container 51 constitutes a second gas flow path 90 for flowing the second gas. The heater 52 is disposed on the outer periphery of the heating container 51. In the present embodiment, a preheating pipe 53 is disposed in the space S so as to penetrate the heating container 51.

The heater 52 is for heating the gas decomposing element 10, and the heater 52 heats the cylindrical MEA 7 and the first gas and the second gas that act on the MEA 7 to a temperature suitable for decomposition. The The preheating pipe 53 is a pipe for preheating the first gas. The first gas is preheated by passing through the preheating pipe 53 before introducing the first gas into the cylindrical MEA 7, and the first gas having a low temperature is suddenly introduced into the cylindrical MEA 7. Eliminates the lack of reaction. As a result, it is possible to improve the decomposition performance and make the gas decomposition element 10 compact. The preheating pipe 53 includes a connection end 53a connected to the pipe from the first gas source, and the downstream side is connected to the gas introduction pipe 45 shown in FIG. As the preheating pipe 53, a heat-resistant pipe, for example, a Ni pipe, an Inconel pipe, or other metal or ceramic heat-resistant and corrosion-resistant pipe can be used.
Although one cylindrical MEA 7 and one preheating pipe 53 are provided for each gas decomposition element 10 in FIG. 3, gas is supplied to a plurality of gas decomposition elements 10 from one preheating pipe. You may comprise as follows. The preheating pipe 53 is heated by using the heater 52 and the heating container 51 for heating the cylindrical MEA 7, and the first gas flowing in the preheating pipe is preheated well.
Although the said heating container 51 is comprised with a heat-resistant material, it is good also as what was comprised thickly with the refractory material and embedded the heater 52. FIG. Moreover, it can also be set as the structure which embed | buried and penetrated the preheating piping 53 in the thickness of the heating container 51 which consists of a thick refractory material.

FIG. 4 is a diagram showing an electrical wiring system of each gas decomposition element 10 when the solid electrolyte layer 1 is oxygen ion conductive. The first gas containing ammonia passes through the preheating pipe 53, and then passes through the gas induction pipe 11k to the innermost part of the inner cylinder of the cylindrical MEA 7 with strict airtightness, that is, the sealing part. It is guided to the vicinity of 44. The entire cylindrical MEA 7 is heated to about 800 ° C. by the heater 52, and the temperature of the first gas is raised while flowing in the gas induction pipe 11k. During this time, ammonia in the first gas is decomposed as 2NH ₃ → N ₂ + 3H ₂ by heating in the gas induction pipe 11k.

  When the cylindrical MEA 7 is used, the porous metal body 11s is used to pass the first gas containing the decomposition gas on the inner surface side and hold the gas induction pipe 11k. From the viewpoint of reducing the pressure loss, as described above, a porous metal plated body, for example, the above-mentioned Celmet (registered trademark) can be used as the porous metal body 11s disposed in the cylindrical flow path 43. . The first gas containing ammonia flows through the first gas flow path from the internal space 42 into the cylindrical flow path 43, and the porous metal body 11s, the Ni mesh sheet 11a, and the porous silver paste coating layer The following ammonia decomposition reaction is performed in contact with the first electrode layer (anode) 2 while passing through the 11 g gap.

Oxygen ions O ²⁻ are generated by an oxygen gas decomposition reaction at the second electrode layer (cathode) 5 and reach the first electrode layer (anode) 2 through the solid electrolyte layer 1. That is, it is an electrochemical reaction when oxygen ions, which are anions, move through the solid electrolyte layer 1.

In the first electrode layer (anode) 2, the following reaction occurs.
(Anode reaction): 2NH ₃ + 3O ²⁻ → N ₂ + 3H ₂ O + 6e ⁻
More specifically, a part of ammonia causes a reaction of 2NH ₃ → N ₂ + 3H ₂ , and this 3H ₂ reacts with oxygen ions 3O ²⁻ to generate 3H ₂ O.
Air, particularly oxygen gas, is introduced into the second electrode layer (cathode) 5 so as to pass through the space S, and oxygen ions decomposed from oxygen molecules in the second electrode layer (cathode) 5 are converted into the first electrode layer. (Anode) 2 is sent to the solid electrolyte layer 1.

In the second electrode layer (cathode) 5, the following reaction occurs.
(Cathode reaction): O ₂ + 4e ⁻ → 2O ²⁻
As a result of the above electrochemical reaction, electric power is generated, and a potential difference is generated between the first electrode layer (anode) 2 and the second electrode layer (cathode) 5, and the anode side current collector 12 performs the anode side current collection. A current I flows to the electric body 11. If a load, for example, a heater 52 for heating the gas decomposition element 10 is connected between the cathode-side current collector 12 and the anode-side current collector 11, a part of the electric power for that purpose can be supplied. it can.

The above is an electrochemical reaction in which oxygen ions, which are anions, move through the solid electrolyte layer 1. For example, barium zirconate (BaZrO ₃ ) is used for the solid electrolyte layer 1 to transfer protons to the first electrode layer (anode). The reaction that is generated in step 2 and moves in the solid electrolyte layer 1 to the second electrode layer (cathode) 5 is also a desirable embodiment of the present invention.

When proton conductive solid electrolyte layer 1 is used, for example, when ammonia in the first gas is decomposed, ammonia is decomposed at first electrode layer (anode) 2 to generate protons, nitrogen molecules, and electrons. The protons are transferred to the second electrode layer (cathode) 5 through the solid electrolyte layer 1 and reacted with oxygen in the second electrode layer (cathode) 5 to generate water (H ₂ O). Since protons are smaller than oxygen ions, the moving speed in the solid electrolyte layer 1 is large. For this reason, a practical decomposition capacity can be obtained while lowering the heating temperature. The thickness of the solid electrolyte layer 1 can also be set to a thickness that can ensure strength.

In the process of decomposing ammonia gas via the solid electrolyte, nitrogen (N ₂ ) and water (H ₂ O) are generated. However, in this embodiment, ammonia gas is also decomposed by heat. In this case, as described above, a reaction of 2NH ₃ → N ₂ + 3H ₂ occurs to generate hydrogen, and the exhaust gas discharged from the connecting member 30 contains hydrogen. In the present embodiment, as shown in FIG. 1, the hydrogen contained in the exhaust gas is guided to the hydrogen separator 71 through the exhaust pipe 65, and the hydrogen is poured out and guided to the gas burner 72. . The gas burner 72 is configured to heat the heating container 51 by burning the hydrogen. By adopting this configuration, it is possible to reduce the power consumption of the heater 52 that heats the heating container 51.

  FIG. 5 is a longitudinal sectional view showing the structure of the upper part of the gas decomposition apparatus 100. The gas induction pipe 11k and the external wiring 11e are connected, and the cylindrical MEA 7, the gas introduction pipe 45, and the exhaust pipe 65 are connected. The form is shown.

  In the present embodiment, the heating container 51 accommodates the lower part of the cylindrical MEA 7 with the axis oriented in the vertical direction, and the upper end of the cylindrical MEA 7 protrudes above the heating container 51 and protrudes. A connecting member 30 for allowing gas to enter and exit is provided at the opening end at the upper end of the projecting portion 41.

  In the connection member 30, the O-ring 33 housed on the inner surface side of the fastening portion 31 b extending from the main body portion 31 to the solid electrolyte layer 1 is in contact with the outer surface of the ceramic solid electrolyte layer 1 that is a fired body. Connected with. The fastening portion 31b of the connection member 30 has an outer diameter that is tapered, and a screw is cut there, and an annular screw 32 is screwed into the screw. By screwing in the direction in which the outer diameter of the annular screw 32 is increased, the fastening portion 31b is fastened from the outer surface, and airtightness by the O-ring 33 can be secured.

  By providing the protrusion 41, a part of the heat conducted from the heating container 51 can be dissipated, and the heat conducted to the O-ring 33 and the connection member 30 can be reduced. For this reason, it can prevent that high temperature acts on the said seal structure or the said connection member 30 via the said cylindrical MEA.

  Inside the connection member 30, a fitting portion 36 is formed in which the base end portion 11 d of the gas guiding pipe 11 k can be fitted with airtightness. As a result, the gas guiding pipe 11k and the connecting member 30 are connected, and the first gas is introduced into the gas guiding pipe 11k.

  The connection member 30 is provided with a gas introduction part 31 a for connection with the gas introduction pipe 45. By fitting the end portion of the gas introduction pipe 45 to the outer periphery of the gas introduction portion 31 a of the connection member 30 and fastening with the fastener 47, a good airtight connection can be obtained. The first gas flows from the gas introduction pipe 45 through the gas introduction part 31a into the gas induction pipe 11k. The first gas that has flowed into the gas induction pipe 11k flows through the internal space 42 to the vicinity of the sealing portion 44 of the cylindrical MEA 7.

  Further, the connection member 30 is provided with a gas discharge part 31 c for connecting to the exhaust pipe 65. By fitting the end portion of the gas exhaust pipe 65 to the outer periphery of the gas discharge portion 31 c of the connection member 30 and fastening with the fastener 67, a connection with good airtightness can be obtained. The first gas that has passed through the cylindrical MEA 7 is discharged to the exhaust pipe 65 through the exhaust space 35 and the gas discharge portion 31 c in the connection member 30. The exhaust pipe 65 is connected to the hydrogen separator 71 as described above, and is configured so that hydrogen in the exhaust gas can be burned by the burner 72.

  By adopting the connection member 30, the first gas is allowed to enter and exit from the same one side position of the cylindrical MEA 7 without mixing the first gas before decomposition and the first gas after decomposition. It becomes possible.

  The main body portion 31 of the connection member 30 is provided with a conductive through portion 37c that penetrates the main body portion 31 while maintaining airtightness, and is coated with a sealing resin 38 or the like in order to maintain airtightness. The conductive penetrating portion 37c is a cylindrical rod, and a screw for screwing the nut 39 is preferably cut in order to make a reliable conductive connection with the external wiring 11e. A conductive wire 37b is joined to the distal end of the conductive through portion 37c in the tube, and the other end 37a of the conductive wire 37b is joined to the outer peripheral portion of the gas induction pipe 11k via an annular fastening tool 34. . By adopting the above configuration, the connection resistance between the gas induction pipe 11k and the external wiring 11e can be reduced.

  On the other hand, the external wiring 12e is circulated around the end of the Ni mesh sheet 12a of the cathode-side current collector 12, and is drawn out to the outside. As a result, a wiring conducting to the second electrode layer (cathode) 5 is provided.

  As the powder material constituting the solid electrolyte layer 1, a solid oxide, molten carbonate, phosphoric acid, solid polymer, or the like can be used. Solid oxides are preferred because they can be miniaturized and are easy to handle. Examples of the solid oxide include oxygen ion conductive SSZ (scandium stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC (samarium stabilized ceria), LSGM (lanthanum gallate), GDC (gadria stabilized ceria), and the like. Should be used. Proton conductive barium zirconate can also be used. Each said powder material can be baked by hold | maintaining at 1000 degreeC-1600 degreeC for about 30 minutes-180 minutes by air | atmosphere atmosphere.

  The first electrode layer (anode) 2 can be formed as a fired body mainly composed of a metal particle chain having an oxidized layer that is surface oxidized and an oxygen ion conductive ceramic. As oxygen ion conductive ceramics, SSZ (scandium stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC (samarium stabilized ceria), LSGM (lanthanum gallate), GDC (gadria stabilized ceria), etc. should be used. Can do.

  When adopting the above SSZ, it is preferable to use one having an average diameter of about 0.5 μm to 50 μm. The firing step can be performed by holding at 1000 ° C. to 1600 ° C. for about 30 minutes to 180 minutes in an air atmosphere. The average diameter of the raw material powder of SSZ is preferably about 0.5 μm to 50 μm. The compounding ratio of the surface-oxidized metal particle chain and SSZ is in the range of 0.1 to 10 in terms of molar ratio.

  The metal of the metal particle chain is preferably nickel (Ni) or one containing Ni (Fe) in Ni. More preferably, it contains a very small amount of titanium (Ti) of about 2 to 10000 ppm.

  The metal particle chain is preferably produced by a reduction precipitation method. The reduction precipitation method for this metal particle chain is described in detail in JP-A No. 2004-332047. The average diameter D of the metal particle chain contained in the first electrode layer (anode) 2 is preferably in the range of 5 nm to 500 nm. The average length L is preferably in the range of 0.5 μm or more and 1000 μm or less. The ratio between the average length L and the average diameter D is preferably 3 or more. However, it may have dimensions outside these ranges.

  The second electrode layer (cathode) 5 is formed from a fired body mainly composed of oxygen ion conductive ceramics. As the oxygen ion conductive ceramic in this case, LSM (lanthanum strontium manganite), LSC (lanthanum strontium cobaltite), SSC (samarium strontium cobaltite), or the like can be used. These powder materials can also be fired under the same conditions as described above.

  FIG. 6 shows a second embodiment of the present invention. In the second embodiment, instead of the gas burner in the first embodiment, a catalyst combustion device 272 is provided to combust hydrogen gas. Note that the configurations of the gas decomposition element 210 and the heating container 251 are the same as those in the first embodiment, and a description thereof will be omitted.

  As shown in FIG. 6, the exhaust gas is guided to the hydrogen separator 271 through the exhaust pipe 265 as in the first embodiment. Then, hydrogen gas is poured out and led to a catalytic combustion device 272 as an auxiliary heating device.

  The catalytic combustion apparatus 272 according to the present embodiment is disposed in a heating vessel 251 that heats the gas decomposition element 210. Thereby, the temperature in the heating container 251 can be made to act on the said hydrogen gas, and can be burned.

  The catalytic combustion device 272 is filled with fibrous platinum or the like. Further, an air supply pipe (not shown) is provided, and the hydrogen can be efficiently burned in the catalytic combustion device 272.

  In the second embodiment, the catalytic combustion device 272 is provided in the heating container 251, but it may be provided in contact with the outer peripheral surface of the heating container 251.

In the above-described embodiment, the first gas containing ammonia gas is decomposed, and the generated hydrogen is guided to the auxiliary heating device that heats the heating container and burned. However, the present invention is not limited to this. For example, CH ₄ can be adopted as the first gas, H ₂ can be generated as the combustible gas, and the heating container can be auxiliary heated.

  In the above-described embodiments, the present invention is applied to a gas decomposition apparatus for the purpose of gas abatement. However, the present invention can be applied to a gas decomposition apparatus not intended for a gas abatement and a cylindrical MEA of an electrochemical reaction apparatus. For example, it can also be used for a cylindrical MEA that constitutes a power generator such as a fuel cell.

  The embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  In addition to high gas decomposition performance, it is possible to provide an energy efficient gas decomposition apparatus and power generation apparatus by reducing the power consumption of the heater that heats the cylindrical MEA.

DESCRIPTION OF SYMBOLS 1 Solid electrolyte layer 2 1st electrode layer (anode)
5 Second electrode layer (cathode)
7 Tubular MEA
DESCRIPTION OF SYMBOLS 10 Gas decomposition | disassembly element 11 Anode side collector 11k Gas induction pipe 12 Cathode side collector 30 Connection member 31c Gas discharge part 41 Projection part 42 Internal space 43 Cylindrical flow path 44 Sealing part 45 Gas introduction pipe 51 Heating vessel 52 Heater 65 Exhaust pipe 71 Hydrogen separator 73 Gas burner (auxiliary heating device)
100 gas decomposition apparatus S space (second gas flow path)

Claims (10)

A cylindrical shape having a cylindrical solid electrolyte layer, a first electrode layer stacked on the inner periphery of the solid electrolyte layer, and a second electrode layer stacked on the outer periphery of the solid electrolyte layer A gas decomposition apparatus configured using MEA (Membrane Electrode Assembly),
While equipped with a heating container that houses and heats the cylindrical MEA,
A gas decomposition apparatus comprising an auxiliary heating device capable of auxiliary heating of the heating container by burning combustible gas in exhaust gas generated by a gas decomposition reaction.   The gas decomposition apparatus according to claim 1, wherein the auxiliary heating device includes a burner that burns the combustible gas.   The gas decomposition apparatus according to claim 1, wherein the auxiliary heating device includes a catalytic combustion device that combusts the combustible gas by a catalytic reaction.   The gas decomposition apparatus according to claim 3, wherein the catalytic combustion apparatus burns the combustible gas using the temperature of the heating container.   The gas decomposition apparatus according to any one of claims 1 to 4, further comprising a gas separation device that separates the combustible gas from the exhaust gas. The gas to be decomposed is a gas containing ammonia,
The gas decomposition apparatus according to any one of claims 1 to 5, wherein the combustible gas produced is hydrogen.   The first electrode layer and / or the second electrode layer is a fired body including a metal particle chain composed mainly of nickel (Ni) and an ion conductive ceramic. The gas decomposition apparatus according to any one of claims 1 to 7.   The gas decomposition apparatus according to any one of claims 1 to 7, wherein the solid electrolyte layer has oxygen ion conductivity or proton conductivity.   A power generator comprising the gas decomposition apparatus according to any one of claims 1 to 8. A cylindrical shape having a cylindrical solid electrolyte layer, a first electrode layer stacked on the inner periphery of the solid electrolyte layer, and a second electrode layer stacked on the outer periphery of the solid electrolyte layer A gas decomposition method performed by a gas decomposition apparatus configured using MEA (Membrane Electrode Assembly),
While heating the cylindrical MEA in a heating container to decompose the gas,
A gas decomposition apparatus for burning the combustible gas in the exhaust gas generated by the gas decomposition reaction to supplementally heat the heating container.

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