JP2010247033A - Gas detoxifying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ammonia decomposing apparatus which is (1) miniaturized and capable of detoxifying a harmful gas efficiently and (2) operable at a low running cost. <P>SOLUTION: The ammonia decomposing apparatus 10 includes an MEA comprising paired electrodes 2 and 3 and an electrolyte 1 held between the paired electrodes. The paired electrodes are provided with flow paths 11 and 12 for introducing a gas respectively. Of the two, at least the flow path of the electrode to which the gas containing a chemical component is introduced is provided with at least one folded part T, and the flow path having the folded part is occupied by a metal porous body 7 or 8 provided with continuous pores. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas abatement apparatus, and more particularly to a gas abatement apparatus that can efficiently decompose harmful gas contained in air, waste gas, etc. with low pressure loss. .

Ammonia is an indispensable compound for agriculture and industry, but it is harmful to humans. Therefore, many methods for decomposing ammonia in water and air have been disclosed. For example, in order to decompose and remove ammonia from water containing high-concentration ammonia, a method in which atomized aqueous ammonia is brought into contact with an air stream to separate ammonia in the air and brought into contact with a hypobromite solution or sulfuric acid Has been proposed (Patent Document 1). In addition, a method of separating ammonia in the air by the same process as described above and combusting with a catalyst is also disclosed (Patent Document 2). Moreover, a method for decomposing ammonia-containing wastewater into a nitrogen and water by using a catalyst has been proposed (Patent Document 3). As for the catalyst for the ammonia decomposition reaction, porous carbon particles containing a transition metal component, manganese composition, iron-manganese composition (Patent Document 3), chromium compound, copper compound, cobalt compound (Patent Document 4), and alumina 3 Platinum (Patent Document 5) and the like supported on a three-dimensional network structure are disclosed. In the method of decomposing ammonia by a chemical reaction using the above catalyst, generation of nitrogen oxides NOx can be suppressed. Furthermore, a method for promoting thermal decomposition of ammonia more efficiently at 100 ° C. or less by using manganese dioxide as a catalyst has been proposed (Patent Documents 6 and 7).
Unlike the case where a large amount of ammonia is decomposed as described above, there is an abatement device whose main purpose is to decompose ammonia or the like, which is an odor component in waste gas, to the order of ppm. For example, waste gas from semiconductor manufacturing equipment usually contains ammonia, hydrogen, etc., and it is necessary to remove it to the ppm order in order to completely remove the odor of ammonia. For this purpose, harmful gases are absorbed by moisture containing chemicals through a scrubber when waste gas is discharged from a semiconductor manufacturing apparatus. The treatment of moisture containing harmful components can be carried out by other methods including the above-described method in a predetermined waste treatment facility.
In addition, in order to obtain an inexpensive running cost without input of energy, chemicals, etc., there has been proposed an exhaust gas treatment of a semiconductor manufacturing apparatus using a hydrogen-oxygen fuel cell decomposition method (Patent Document 8).

JP-A-7-31966 Japanese Patent Laid-Open No. 7-116650 Japanese Patent Laid-Open No. 11-347535 JP-A-53-11185 JP 54-10269 A JP 2006-231223 A JP 2006-175376 A JP 2003-45472 A

  According to the above-described method using a chemical such as a neutralizing agent (Patent Document 1), a method of burning (Patent Document 2), a method using a thermal decomposition reaction using a catalyst (Patent Documents 3 to 7), etc. Is possible. Scrubbers can also be detoxified to the order of ppm, such as ammonia. However, the above method has a problem in that it requires chemicals and external energy (fuel), and requires periodic replacement and maintenance of the catalyst, resulting in high running costs. In particular, maintenance-free components are not allowed for a long period of time. In addition, the apparatus becomes large and, for example, when it is additionally provided in existing equipment, the arrangement may be difficult. For the hydrogen-oxygen fuel cell decomposition method, if exhaustion is thoroughly performed down to the ppm order, a long exhaust gas flow path is required at the fuel electrode, which increases pressure loss → suppresses pressure loss by increasing the size of the device. Is called. In Japan, an increase in the size of the apparatus often has a great disadvantage in practical use and should be avoided.

  An object of the present invention is to provide a gas abatement apparatus that can (1) be small, efficiently remove harmful gas to a harmless level, and (2) operate at a low running cost.

  The gas abatement apparatus of the present invention detoxifies chemical components in a gas by an electrochemical reaction. This gas abatement apparatus includes a pair of electrodes and an MEA composed of an electrolyte sandwiched between the pair of electrodes, and each of the pair of electrodes is provided with a flow path for introducing a gas. Of these, at least one folded portion is provided in the flow path of the electrode into which a gas containing at least a chemical component is introduced, and the flow path having the folded portion is occupied by a porous metal body having continuous pores. It is characterized by that.

According to the above configuration, (E1) By using a flow path with a folded portion, the entire area of the device is small (by turning the flow path), the efficiency per area is increased, and harmful components are harmless. Can be broken down to level. Further, the folded portion promotes gas turbulence. Furthermore, (E2) by disposing a metal porous body in the flow path, passage through a gas containing harmful components is prevented, and the turbulent state of the gas is greatly promoted. By making the gas turbulent, rather than letting it pass as a laminar flow, the opportunity, time, and the like of the gas contacting the both-side electrodes can be lengthened. Thereby, the electrochemical reaction efficiency per electrode unit area can be increased. Since this porous metal body is a conductor, it can be used as a current collector for electrodes, and can facilitate the transfer of charges (electrons) accompanying the decomposition of harmful components. This can prevent the flow of electric charges from becoming a bottleneck for electrochemical reactions.
The greater the number of turns (number of turns), the longer the flow path length and the more beneficial the concentration of harmful components is. However, if the number is too large, the pressure loss increases, resulting in MEA deformation and energy efficiency. May cause deterioration, noise, etc.
In addition, said metal porous body can be arrange | positioned so that the said flow path may be occupied not only in the flow path with a folding | returning part but in the flow path of the reverse polarity electrode which makes a pair.
The running cost for continuing the electrochemical reaction is about the electricity cost of the heater required to heat the gas abatement apparatus to about 800 ° C., and maintenance costs are not required. For this reason, it is a very low running cost compared with the conventional one. Further, since a large amount of gas can be removed efficiently by heating at about 800 ° C., the catalyst in the paired electrodes, the flow path with the folded portion, etc., a large-scale apparatus is unnecessary.

  Said metal porous body is a metal plating body, and can make a porosity 95% or more. This makes it possible to obtain much better air permeability than that obtained by compacting and sintering metal particles and metal fibers. If the porosity is less than 95%, the pressure loss becomes large, and if forced circulation by a pump or the like is performed, the energy efficiency is lowered, and bending deformation or the like occurs in the ion conductive material or the like. Although the upper limit of the porosity is not particularly provided, when the porosity exceeds 0.98, the electrical conductivity is lowered and the current collecting function is lowered.

Of the metal porous body, when the pore size x (mm), the specific surface area and ^{y (m 2 / m 3)} , it is possible to satisfy 400 ≦ (x-0.3) y , a. As a result, an increase in pressure loss can be prevented while obtaining the effect (E2). In order to more strictly prevent an increase in pressure loss, 600 ≦ (x−0.3) y is preferable. The upper limit of (x−0.3) y is not particularly required, but can be, for example, 3000 as an upper limit in order to ensure the effect of (E3).

  The MEA is a set of two, and the pair of MEAs has the same polarity electrodes facing each other, and a flow path including a folded portion is sandwiched between the opposite polar electrodes, It can be a road. As a result, electrochemical reaction of harmful components to extremely low levels is achieved in a shorter flow path than expected while flowing the gas containing the chemical component (gas) to be decomposed into the flow paths on both sides to prevent an increase in pressure loss. Can be disassembled.

  In the above two MEAs, the opposite electrode channel is provided with a reverse-polar channel for introducing gas to an electrode having a polarity opposite to that of the electrode sandwiching the both-side electrode channel, and the cross-sectional area of the both-side electrode channel is The configuration may be equal to or larger than the larger cross-sectional area of the reverse flow paths of the two MEAs. As a result, the pressure loss can be reduced while increasing the flow rate of the gas containing harmful components to be decomposed. In this case, the detoxified chemical component is decomposed to a very low level to a low concentration (because degradation reaction at a low concentration level is a problem), so the other side required for the electrochemical reaction The amount of gas may be small, at least near the outlet. For this reason, considering the reduction of the pressure loss of the both-side electrode flow channel through which the gas containing the toxic chemical component flows first, the above configuration can be obtained by imposing the condition that the entire thickness is not increased excessively.

  A plurality of sets of gas abatement devices formed by two MEAs are stacked, and adjacent sets, electrodes having opposite polarity to electrodes sandwiching both-side electrode channels sandwich opposite electrode channels. You can Accordingly, the gas abatement apparatus having a simple structure can be obtained without increasing the number of parts, and the pressure loss can be reduced with respect to the flow of the counterpart gas. Moreover, it can manufacture efficiently.

  It can be set as the structure which does not have an insulation partition sheet between several laminated | stacked MEA. As a result, it is possible to obtain a reduction in the number of parts, a reduction in the thickness of the gas abatement apparatus, a reduction in pressure loss, and the like.

  A gas containing ammonia is introduced into the flow path having the folded portion, and air can be introduced into the flow path of the electrode opposite to the flow path. Thereby, the gas containing ammonia can be operated efficiently and at a low running cost.

  According to the gas abatement apparatus of the present invention, (1) it is small and efficient, it can remove harmful gas to a harmless level, and (2) it can be operated at a low running cost.

It is a perspective view of the external appearance of the ammonia decomposition apparatus in Embodiment 1 of this invention. It is a top view which shows the flow path of the ammonia containing gas of the ammonia decomposition apparatus of FIG. It is a fragmentary sectional view containing the ammonia containing gas inlet_port | entrance of the ammonia decomposing apparatus of FIG. It is an expanded sectional view of the part containing one MEA of the part corresponding to the channel C1 of FIG. It is a figure for demonstrating the electrochemical reaction in an anode. It is a figure for demonstrating the electrochemical reaction in a cathode. It is a figure for demonstrating the method to manufacture the plating porous body of the cathode collector of an ammonia decomposition device, and an anode collector. It is a figure which shows the specific example of the method of performing an alloying process to a plating porous body, (a) is aluminizing, (b) is a figure which shows chromizing. It is a figure which shows the relationship between the specific surface area and pore diameter of Ni plating porous body manufactured with the method of FIG. It is sectional drawing containing the inlet_port | entrance of the ammonia containing gas of the ammonia decomposition apparatus in Embodiment 2 of this invention. FIG. 11 is an enlarged cross-sectional view of a portion including a set of MEAs corresponding to the channel C1 of FIG. It is a figure which shows the electrochemical reaction in the anode side flow path of the ammonia decomposition apparatus of FIG. It is a figure which shows the electrochemical reaction in the anode side flow path of the ammonia decomposition apparatus of a parallel laminated structure. It is a figure which shows the part of a multi-layer laminated structure by making two MEA of the ammonia decomposing apparatus shown in FIG. 10 into one set. It is a figure explaining the electrochemical reaction in the cathode side flow path in the multiple laminated structure of FIG. It is a figure which shows a part when a plurality of parallel laminated structures are stacked. It is a figure explaining the electrochemical reaction in the cathode side flow path in the structure of FIG. In an Example, it is a figure which shows the change of the ammonia concentration along the flow path of an ammonia decomposition apparatus.

(Embodiment 1-one-sided electrode structure)
FIG. 1 is a diagram showing an ammonia decomposition apparatus 10 which is a gas abatement apparatus in Embodiment 1 of the present invention. In the ammonia decomposing apparatus 10, ammonia in the ammonia-containing gas is decomposed by an electrochemical reaction, particularly a fuel cell reaction. An ammonia-containing gas is introduced from the inlet 61 into the fuel electrode (hereinafter referred to as the anode) of the fuel cell, and air is introduced from the inlet 71 into the air electrode (hereinafter referred to as the cathode). By the electrochemical reaction described below, ammonia in the ammonia-containing gas is decomposed into nitrogen and water and released from the outlet 62 together with other gases. In addition, oxygen also participates in the electrochemical reaction with respect to air, and the remaining nitrogen and the like are released from the outlet 72. After ammonia is decomposed, the ammonia concentration in the gas discharged from the outlet 62 is detoxified to the order of ppm or less.
Thus, the abatement apparatus is different from the fuel cell in that the decomposition target component in the gas associated with the fuel is decomposed to an extremely low concentration level. In fuel cells, attention is focused on power generation efficiency, and it is assumed that the concentration of components to be decomposed in gas is above a predetermined level. In the present embodiment, the component in the gas corresponding to the fuel is decomposed. However, the present invention is not limited to this. For example, the gas corresponding to the air is not air itself, but another component (for example, NOx) or the component You may decompose | disassemble the said component in the other gas or air containing. The form of decomposing specific components in the gas in contact with the cathode will be described in Table 1 at the end.
In FIG. 1, electric power can be taken out from an anode terminal that is conductively connected via an anode (not shown) and an anode current collector, and a cathode terminal that is conductively connected via a cathode and a cathode current collector. The ammonia decomposing apparatus 10 is heated to about 800 ° C. in order to obtain a practical electrochemical reaction rate. You may supply the electric power taken out from the cathode terminal and the anode terminal to this heater for a heating. Whatever load is applied between the cathode terminal and the anode terminal, in order to cause and sustain the electrochemical reaction of ammonia decomposition, electrons generated at the anode are transferred from the anode terminal to the cathode terminal. It is necessary to conduct through the load.

FIG. 2 is a view showing a flow path of the ammonia decomposing apparatus 10 shown in FIG. The flow path 12 has a turn-back portion T, and forms channels C1 to C7 that reciprocate alternately to increase the flow path length. The flow path 12 with the folded portion T is an anode side flow path 12 for introducing an ammonia-containing gas into the anode, and a metal porous body 8 having a metal plating body as a skeleton is disposed so as to occupy the flow path. Yes. This metal porous body also serves as the anode current collector 8. The ammonia decomposition apparatus 10 is formed by laminating a plurality of MEAs, and each MEA is partitioned by an insulating partition sheet (not shown). Air is introduced into the cathode paired with the anode facing the flow path having the folded portion T shown in FIG. 2, but the folded portion may not be provided for the flow path into which the air is introduced. A folded portion may be provided. Here, the flow path for introducing air will be described as having a turn-back portion T, as in the flow path for introducing ammonia-containing gas.
By having the turn-back portion T, the flow path length can be increased while the area of the MEA is small, and the ammonia concentration in the gas can be reduced to a harmless level, for example, on the order of ppm. The channel wall 15 separating the reciprocating channels should be as thin as possible in order to suppress pressure loss. In the anode side flow path 12 shown in FIG. 2, the number of the turn-back portions T, that is, the number of turns is six. As the number of turns increases, the length of the flow path becomes longer and the decomposition reaction can be caused to occur longer. However, since the pressure loss increases, it is preferable to make it within an allowable range.

FIG. 3 is a cross-sectional view of a portion including the ammonia-containing gas inlet 61 of FIG. In FIG. 3, the gas flows perpendicularly to the paper surface in the channel C1 and the like. Five MEAs are stacked. On the anode side of each MEA, the anode current collector 8 is disposed so as to occupy the anode-side flow path 12 for each channel in which the anode current collector 8 reciprocates alternately, and the ammonia-containing gas introduced from the inlet 61 flows into this flow path. It is. Further, a cathode current collector 7 is disposed on the cathode side of each MEA so as to occupy the cathode side flow path 11 for each channel that reciprocates alternately. The inlet side shown in FIG. The air introduced from 71 is flowed. One set of anode current collector 8 / MEA / cathode current collector 7 is used as a set, and each set is separated by an insulating partition sheet 13. The insulating partition sheet 13 is necessary for preventing a short circuit between the anode and the cathode and isolating the ammonia-containing gas from the air. In the anode side channel 12, the electrochemical reaction in the anode is performed only on one of the upper and lower surfaces defining the channel (the lower surface in FIG. 3), and also in the cathode side channel 11, the electrochemical reaction in the cathode. Is performed only on one of the upper and lower surfaces defining the flow path (the upper surface in FIG. 3). This is because in the arrangement of the MEA shown in FIG. 3, each of the channels 11 and 12 is a one-side electrode channel having an electrode only on one side. This embodiment is an example in the case of a one-side electrode structure having a one-side electrode flow path. The cathode current collector 7 is electrically connected to the cathode terminal 7a, and the anode current collector 8 is electrically connected to the anode terminal 8a.
In the anode-side channel 12 and the cathode-side channel 11, a metal porous body that also serves as a current collector is disposed. This metal porous body is required to have electrical conductivity and air permeability, and in particular, the air permeability is required to hardly cause pressure loss. Such a porous metal body with high air permeability that can suppress pressure loss is difficult to obtain with a sintered body of metal particles or metal fibers. As a metal porous body having the above-mentioned characteristics, for example, there is a metal-plated metal porous body in which triangular skeletons are three-dimensionally connected to form continuous pores. As a typical material, for example, Celmet manufactured by Sumitomo Electric Industries, Ltd. (Trademark registration) can be used. The electrochemical reaction and the metal porous body will be described in detail later.

FIG. 4 is a cross-sectional view of a portion including the channel C1 and a height (thickness) of one MEA. An anode 2 and a cathode 3 are disposed across the oxygen ion conductive electrolyte 1. An anode current collector 8 is disposed outside the anode 2, and a cathode current collector 7 is disposed outside the cathode 3. The anode 2 is a sintered body mainly composed of a metal particle chain 21 having a surface oxide layer and an ion conductive ceramic (metal oxide) 22 and is a porous body through which a fluid can flow. The cathode 3 is also a porous body through which a fluid can circulate, and includes, for example, a metal particle chain 31 having a surface oxide layer, an ion conductive ceramic 32, and silver (Ag) 33 as main components. It can be a sintered body. The anode current collector 8 and the cathode current collector 7 are both metal porous bodies having the above-mentioned continuous pores.
The electrolyte 1 may be anything as long as it has ionic conductivity, such as a solid oxide, molten carbonate, phosphoric acid, a solid polymer, and an electrolytic solution. The material of the electrolyte 1 will be specifically described later.
In FIG. 4, the ammonia-containing gas is introduced into the anode 2 in a turbulent state in the channel C <b> 1 (12) by the anode current collector 8 made of a metal porous body. Air is introduced into the cathode 3 in a turbulent state in the cathode-side channel 11 by the cathode current collector 7 made of a metal porous body. The introduced air or ammonia-containing gas undergoes a predetermined reaction at the cathode 3 or the anode 2 and is then released to the outside. This electrochemical reaction is an electrochemical reaction accompanied by power generation, and power can be extracted from the anode current collector 8 and the cathode current collector 7 and supplied to the load. The load may be a heating device (not shown), for example, a heater, built in the ammonia decomposition apparatus 10.
In the case of the ammonia decomposing apparatus 10, in order to shorten the passage time of oxygen ions in the electrolyte 1 and to secure the electrochemical reaction speed at each electrode, the main point is to use a heater or the like to promote the entire electrochemical reaction. For example, it is heated to 600 ° C. to 950 ° C. (it may be used at other temperatures). As described above, a gas having a high oxidizing power including oxygen atoms is introduced into the cathode 3 and the cathode current collector 7. Metals exposed to a gas having high oxidizing power at a high temperature of 600 ° C. to 950 ° C. are oxidized by the gas except for special metals, and become unusable after a predetermined period. Forms in which the cathode current collector becomes unusable include clogging due to increased oxidation (decreased air permeability, increased pressure loss), decreased current collecting performance, and the like. Also in the cathode, the same deterioration in air permeability and conductivity due to high-temperature oxidation occurs.
Since a reducing gas flows on the anode side such as the anode current collector, the problem of high-temperature oxidation hardly occurs.

FIG. 5 is a diagram for explaining the role of the material constituting the anode 2. The anode 2 is composed of a sintered body of a surface-oxidized metal particle chain 21 and an oxygen ion conductive ceramic 22. The metal of the metal particle chain 21 is preferably Ni. Ni may contain a little iron (Fe). More preferably, Ti contains a trace amount of about 2 to 10000 ppm.
In the anode 2, ammonia reacts with oxygen ions that have passed through the electrolyte 1 from the cathode 3 by the anode reaction of 2NH ₃ + 3O ^{2 −} → N ₂ + 3H ₂ O + 6e ⁻ , and is decomposed into nitrogen, water vapor, and electrons. The above-described anode reaction occurs at a place where the oxide layer 21b, the Ni grain chain 21a, and the oxygen ion conductive ceramic 22 meet. Electrons generated by the anode reaction conduct through the Ni particle chain 21a and flow to an external circuit or a load. Since the Ni grain chain 21a is elongated, it has excellent electron conductivity and has an effect of preventing the electrochemical reaction from being hindered in terms of electron transfer. After the decomposition reaction, nitrogen and water vapor are discharged to the outside from the outlet 62 shown in FIG. 2 together with unreacted ammonia and the remaining gas components. The electrons are conducted to the cathode 3 via an external circuit or a load. At the cathode, oxygen ions are generated and sent to the electrolyte 1 by the cathode reaction, O ₂ + 2e ⁻ → 2O ²⁻ .
As described above, the Ni particle chain 21 with the surface oxide layer in the anode 2 has a strong catalytic action that promotes the anode reaction in response to the cathode reaction in the cathode 3. For this reason, it is possible to cause a much more efficient decomposition reaction than when ammonia is simply brought into contact with platinum particles at a high temperature for decomposition.

FIG. 6 is a diagram for explaining the role of the materials constituting the cathode 3 and the cathode current collector 7. The cathode current collector 7 is formed of a porous body having continuous pores made of nickel or a nickel alloy, or a surface layer of a metal porous body of nickel or a nickel alloy (chrome) in order to improve the above-described high-temperature oxidation resistance. (Cr), aluminum (Al) and other metals). This enhances the high temperature oxidation resistance.
The cathode 3 in the present embodiment is a porous body having a void 3h, and is composed of a metal particle chain 31 such as Ni having an oxide layer, Ag particles 33, and ceramics 32 through which oxygen ions pass. Among them, the Ag particles 33 and the metal particle chain 31 with an oxide layer have a catalytic function for greatly promoting the cathode reaction O ₂ + 2e ⁻ → 2O ²⁻ . The Ni grain chain 31a is excellent in the conductivity of electrons exerted on the cathode reaction, and is not restricted in terms of electron transfer.
As for the above-described metal particle chain 31 such as Ni, similarly to the cathode current collector, the catalytic action and conductivity are deteriorated due to high-temperature oxidation. For this reason, it is preferable to improve the high-temperature oxidation resistance of Ni grain chains by alloying metal parts or forming alloy layers.

  Next, the contents of the MEA constituting the fuel cell will be described. The MEA includes an electrolyte 1 and an anode 2 and a cathode 3 that sandwich the electrolyte 1. The electrolyte 1 may be anything as long as it has ionic conductivity, such as a solid oxide, molten carbonate, phosphoric acid, a solid polymer, and an electrolytic solution. Solid oxides are preferred because they can be miniaturized and are easy to handle. As the solid oxide, SSZ (scandium stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC (samarium stabilized ceria), LSGM lanthanum gallate), or the like is preferably used.

  The anode 2 is preferably a sintered body mainly composed of a metal particle chain 21 that has been oxidized on the surface and has an oxide layer, and an oxygen ion conductive ceramic 22. As the oxygen ion conductive ceramic 22, the above-described SSZ, YSZ, SDC, LSGM, or the like can be used.

  The cathode 3 is a sintered body mainly composed of a Ni particle chain 31 having an oxidized layer that is surface oxidized, an oxygen ion conductive ceramic 32, and silver (Ag) 33. As the oxygen ion conductive ceramic 32, it is preferable to use LSM (lanthanum strontium manganite), LSC (lanthanum strontium cobaltite), SSC (samarium strontium cobaltite) or the like. The Ni grain chain is made of Ni as the metal of the metal grain chain and is relatively easy to manufacture and is known. Further, the conductive part (metal part covered with the oxide layer) of the Ni grain chain may be Ni alone, or Ni may contain Fe.

1. Current collector (metal porous body by metal plating)
Next, an example of a method for producing a continuous pore porous body (hereinafter referred to as a plated porous body) having a skeleton formed of a metal plating body used for the anode current collector 8 and the cathode current collector 7 Will be described. FIG. 7 is a diagram showing an example of a method for producing a plated porous body. In FIG. 7, first, a foamed resin is prepared by foaming a resin such as urethane. Subsequently, the pore continuation process which continues the foamed pore is performed. The pore continuation process is a process called a film removal process, and is a known process for removing the cell membrane (bubble film) of the polyurethane foam. As a known film removal treatment, an alkaline treatment method in which a polyurethane foam is immersed in an alkali-concentrated solution and the cell membrane is dissolved and removed by hydrolysis, or water is impregnated into the polyurethane foam by a penetrant. Wet overheating method that destroys cell membrane by volume expansion of water by heating above ℃ and polyurethane foam is housed in a sealed container, and the sealed container is filled with gas composed of hydrogen, oxygen, etc. There is a heat treatment (explosion method) that breaks the cell membrane. By the above film removal treatment, most of the cell membrane is removed from the polyurethane foam, and only the skeleton is formed. Thereafter, a conductive carbon film is attached to the pore inner walls, or a conductive thin film is formed by electroless plating or the like. Next, a metal plating layer is formed on the conductive carbon film or the conductive thin film by electroplating. This metal plating layer becomes the skeleton of the pore body. For metal plating, a plating solution containing nickel ions is preferably used to form a Ni plating layer. Ni has high-temperature oxidation resistance in the above-mentioned low temperature range, and the formation of a plating layer is easy. Next, the resin is dissipated by heat treatment to leave only the metal plating layer, thereby forming a Ni-plated porous body.
In order to obtain oxidation resistance performance at a higher temperature like the cathode current collector 7, the Ni plating porous body is subjected to an alloying treatment as described above. This alloying treatment is performed by introducing Cr, Al, and other metals from the outside into the surface layer. Usually, alloying is stopped only on the surface layer to form a plated porous body with an alloyed surface layer. Although not shown in FIG. 7, nickel ions and other metal ions can be dissolved in the plating solution to make the plated body a nickel alloy. As such, a nickel alloy skeleton may be formed by directly forming an alloy plating layer.

FIG. 8 is a diagram showing a specific example of the Al or Cr addition treatment. FIG. 8A is a specific example of aluminizing. In this method, a Ni-plated porous body (indicated by “Me” in FIG. 8A) is embedded in a steel case together with a preparation composed of Fe—Al alloy powder and NH ₄ Cl powder. Next, the case is sealed, and the sealed case is charged into a furnace and heated to 900 ° C. to 1050 ° C. Thereby, an Al diffusion / permeation layer can be obtained, and high-temperature oxidation resistance, wear resistance, and the like can be improved. FIG. 8B is a specific example of chromizing. In this method, a Ni-plated porous body (Me) is embedded in a case together with a preparation composed of Cr powder, Al ₂ O ₃ powder and NH ₄ Cl powder. A Cr diffusion / permeation layer can be obtained by heating to 900 ° C. to 1100 ° C. in a furnace while passing H ₂ gas or Ar gas through the case. This Cr diffusion layer can also improve the high temperature oxidation resistance. In FIG. 8, only the powder method is shown for both aluminizing and chromizing, but Al or Cr can be diffused and permeated using an existing arbitrary method such as a gas method or a molten salt method.

FIG. 9 shows the relationship between the specific surface area (y: m ² / m ³ ) and the pore diameter (x: mm) of the Ni-plated porous body produced by the method shown in FIG. The small black circles in FIG. 9 are actually measured values. It can manufacture with said method over hole diameter 0.45mm-3.2mm. The measured value has a large specific surface area at the same pore diameter as compared with the hyperbola of (x−0.3) y = 400 or 600. When the value of (x−0.3) y is large, the pressure loss is reduced while maintaining the function of contacting the gas introduced into the cathode current collector 7 and sending the gas into the cathode 3 in a turbulent state. Produces a possible effect. For this reason, it is preferable to satisfy 400 ≦ (x−0.3) y. More preferably, 600 ≦ (x−0.3) y. Since there is a risk that a bad effect (such as a decrease in conductivity) may occur, the upper limit is preferably about 3000, more preferably about 2000.
In the Ni-plated porous body, the size of the pores and the thickness (thinness) of the skeleton can be adjusted independently. For this reason, the Ni-plated porous body can easily reduce the pressure loss while obtaining sufficient conductivity and sufficient turbulent flow generation action.

2. Cathode and anode metal particle chain 21, 31
The metal particle chain bodies 21 and 31 are preferably manufactured by a reduction precipitation method. The reduction precipitation method of the metal particle chain bodies 21 and 31 is described in detail in Japanese Patent Application Laid-Open No. 2004-332047. The reduction precipitation method introduced here is a method using trivalent titanium (Ti) ions as a reducing agent, and the precipitated metal particles (Ni particles and the like) contain a small amount of Ti. For this reason, it can identify with what was manufactured by the reduction | restoration precipitation method by trivalent titanium ion by quantitatively analyzing Ti content. By changing the metal ions present together with the trivalent titanium ions, desired metal grains can be obtained. In the case of Ni, Ni ions are allowed to coexist. When a small amount of Fe ions is added, a Ni grain chain containing a small amount of Fe is formed.
In order to form a chain, the metal must be a ferromagnetic metal and have a predetermined size or more. Since both Ni and Fe are ferromagnetic metals, a metal particle chain can be easily formed. The size requirement is that the ferromagnetic metal forms a magnetic domain and bonds with each other by magnetic force, and in the combined state, the metal is deposited → the growth of the metal layer occurs, and the entire metal body is integrated. ,is necessary. Even after metal grains of a predetermined size or more are bonded by magnetic force, metal deposition continues, for example, the neck at the boundary of the bonded metal grains grows thicker together with other portions of the metal grains. The average diameter D of the metal particle chain bodies 21 and 31 contained in the anode 2 or the cathode 3 is preferably in the range of 5 nm or more and 500 nm or less. 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 metal particle chain 31 of the cathode 3 is preferably used for a low temperature range, for example. Similar to the cathode current collector 7, the metal particle chain 31 for the high temperature region is preferably subjected to an alloying treatment such as aluminizing or chromizing as shown in FIG. 5. That is, the Ni particle chain 31 contained in the cathode 3 of the ammonia decomposition apparatus 10 used in a high temperature range of 600 ° C. to 950 ° C. is provided with an enriched layer such as Cr or Al for high temperature oxidation resistance. preferable. The plated body of the alloy constituting the metal porous body may be directly formed by plating.

3. Surface oxidation Both the Ni grain chain 21 in the anode 2 and the Ni grain chain 31 in the high temperature region cathode and the low temperature region cathode 3 are surface oxidized in order to enhance the catalytic action for promoting the electrochemical reaction. It is better.
Three types of surface oxidation treatments are suitable: (i) heat treatment oxidation by a vapor phase method, (ii) electrolytic oxidation, and (iii) chemical oxidation. In (i), it is good to process at 500-700 degreeC for 1 to 30 minutes in air | atmosphere. Although it is the simplest method, it is difficult to control the oxide film thickness. In (ii), surface oxidation is performed by applying a potential to about 3 V with reference to a standard hydrogen electrode and performing anodization. However, the oxide film thickness can be controlled by the amount of electricity according to the surface area. However, when the area is increased, it is difficult to uniformly form an oxide film. In (iii), the surface is oxidized by being immersed in a solution in which an oxidizing agent such as nitric acid is dissolved for about 1 to 5 minutes. Although the oxide film thickness can be controlled by time, temperature, and type of oxidizer, cleaning of chemicals is troublesome. Either method is suitable, but (i) or (iii) is more preferred.
A desirable thickness of the oxide layer is 1 nm to 100 nm, and more preferably 10 nm to 50 nm. However, it may be outside this range. If the oxide film is too thin, the catalyst function will be insufficient. In addition, even a slight reducing atmosphere may cause metallization. On the other hand, if the oxide film is too thick, the catalytic property is sufficiently maintained, but on the other hand, the electronic conductivity at the interface is impaired and the power generation performance is lowered.

4). Sintering The average diameter of the raw material powder of SSZ22 or LSM32 contained in the anode 2 or the cathode 3 is about 0.5 μm to 50 μm. The compounding ratio of the surface-oxidized metal particle chain 21, 31 and SSZ22, LSZ32 is in the range of 0.1 to 10 in terms of molar ratio.
A sintering method is performed by hold | maintaining for 30 minutes-180 minutes, for example in air | atmosphere atmosphere at the temperature of 1000 to 1600 degreeC.
The cathode 3 is composed of a sintered body such as a metal particle chain 31 with an oxide layer, LSM, and Ag particles 33. The average diameter of the Ag particles is preferably 10 nm to 100 nm. The compounding ratio of silver and LSM is preferably about 0.01 to 10.
The time of surface oxidation of the chain metal powder may be before or after the formation of the sintered body.

  In the ammonia decomposing apparatus 10 of the present embodiment, the folded portion T is provided in the flow path, and the flow path is occupied by the highly porous metal porous bodies 8 and 7 formed by metal plating. Thereby, even if it is MEA or a reaction part of a small area, a flow path length can be lengthened, the turbulent flow promotion effect | action of the metal porous bodies 8 and 7 can also be obtained, and ammonia decomposition can be performed to a required level. At this time, the increase in pressure loss caused by the extension of the flow path length can be mitigated by the metal porous bodies 8 and 7 by metal plating having excellent air permeability.

(Embodiment 2-Double-sided electrode structure-)
FIG. 10 is a diagram showing the ammonia decomposing apparatus 10 according to the first embodiment of the present invention, and corresponds to FIG. 3 according to the first embodiment. However, in FIG. 10, the thickness (height) is a partial cross-sectional view of only two MEAs. The flow paths 11 and 12 of the ammonia decomposing apparatus 10 shown in FIG. 10 have the same folded portion T as in FIG. 2 and are formed by channels C 1 and the like that reciprocate alternately separated by the channel wall 15. A feature of the present embodiment is that the anode 2 is disposed on both the upper and lower surfaces of the anode-side channel 12. That is, the two MEAs are such that the anodes 2 of the same polarity are opposed to each other, the flow channel 12 is sandwiched between them, and the flow channel 12 is a double-sided electrode flow channel. An ammonia-containing gas introduced from the inlet 61 is introduced into the both-side electrode channel 12. In addition, air that is a counterpart gas is introduced into the cathode-side channel 11 on the opposite side of each MEA. The cross-sectional area of the both-side electrode flow path 12 is larger than any of the cathode side flow paths 11 as can be seen from the cross section of the channel C1 and the like. This makes it possible to suppress pressure loss while flowing a large amount of ammonia-containing gas whose concentration has been reduced to an extremely low level. Since the ammonia concentration is reduced to a very low level, the amount of air required for the electrochemical reaction is small. For this reason, the magnitude relation of a cross-sectional area as shown in FIG. 10 is brought about.

11 is a partial cross-sectional view including the MEA and the flow path of FIG. As described above, two MEAs are arranged across the both-side electrode flow path C1 (12) occupied by the anode current collector 11 which is a metal porous body. An ammonia-containing gas is passed through the channel C1 and contacts the anode 2 to decompose ammonia. Moreover, the two cathode side flow paths 11 located outside the two MEAs are occupied by the cathode current collector 7, and air is introduced therein.
The point of the ammonia decomposing apparatus 10 in the embodiment of the present invention is that the anodes 2 of the two MEAs are arranged so as to face each other with the ammonia-containing gas channel (both-side electrode channel) 12 in between. As shown in FIG. 12, in this arrangement, ammonia decomposes by causing an electrochemical reaction to proceed because the wall surface is the anode 2 on both the upper surface and the lower surface that define the both-side electrode flow path 12. For this reason, an electrochemical reaction proceeds on the lower wall and the upper wall 2.
FIG. 13 is a diagram showing a flow path (one-side electrode flow path) when the same surfaces of the MEAs are aligned on the same side and stacked in parallel for comparison. In such a structure in which MEAs are stacked in parallel, it is appropriate to compare with the flow path of FIG. 12 assuming that there are two flow paths 12 shown in FIG. Although ammonia flows through the flow path 12, in the case of FIG. 13, it decomposes only at the upper wall, which is the anode 2, and does not decompose at the lower wall of the insulating partition sheet 13, but simply contacts as gas. There are two such channels.
Compared with the case where the both-side electrode flow path in FIG. 12 is one and the case where there are two one-side electrode flow paths in FIG.
(1) If a large amount of ammonia is introduced into these flow paths, the total area of the decomposition site (anode 2) is the same in both cases, and the total amount of ammonia decomposed is not very different. For this reason, for example, when the power generation efficiency of the fuel cell is considered as a problem, both of them produce results that are not significantly different.
(2) However, when detoxifying (decomposing) ammonia to an extremely low concentration, for example, ppm order, the required length of MEA is due to the presence of ammonia flowing in contact with the wall (insulating partition sheet 13) without being reacted. It will be long. This is because there are walls that allow unreacted conditions. In order to detoxify to an extremely low concentration, it is necessary to peel off unreacted ammonia from the wall and to contact the opposite wall (anode 2). If there is no wall that remains unreacted, ammonia can pass through the wall freely, so that the decomposition reaction does not have to stagnate. That is, like the double-sided electrode flow path, the interval is double, but both the upper wall and the lower wall are the anodes 2, and when the decomposition proceeds, there is no part that does not react and contacts the wall. The required length of the MEA to be disassembled is shortened.
(3) Since the both-side electrode flow path 12 for flowing the ammonia-containing gas does not need to be provided with the insulating partition sheet 13 as compared with the two one-side electrode flow paths with the insulating partition sheet 13, the pressure loss is easily reduced. For this reason, it is advantageous also in terms of pressure loss.
According to the above (1) and (2), in the device that removes harmful components to an extremely low concentration level, the double-sided electrode structure has a great effect on downsizing the device, particularly shortening the flow path length. Moreover, (3) It is easy to suppress pressure loss.

(Multi-layer laminated structure)
FIG. 14 is a diagram showing a part of a multi-layer stack structure in which a plurality of sets are stacked with the two MEAs in FIG. 10 as one set. In the multi-layer laminated structure of FIG. 14, ammonia is decomposed in the anode 2 on the upper wall and the lower wall in the flow path (both electrode flow paths) 12 of one channel, which is the same as that of the set of FIG. 10. . And in the flow path 11 of one channel into which oxygen is introduced, oxygen is decomposed at the cathode 3 on the upper wall and the lower wall. That is, the channel 11 is also a double-sided electrode channel, and as shown in FIG. 15, oxygen reacts with the cathode 3 on the upper and lower walls of the channel 11 to become oxygen ions O ²⁻ .
On the other hand, the multi-layer laminated structure in which MEAs are laminated in parallel is isolated by an insulating partition sheet 13 as shown in FIG. For this reason, both the flow path 12 and the flow path 11 become a one-side electrode flow path. In the flow path 11 of FIG. 16, as shown in FIG. 17, it decomposes | disassembles in the cathode 3 of an upper wall, and it contacts a wall with oxygen in the insulating partition sheet 13 of a lower wall.

  In the structure shown in FIG. 14, the upper wall of the flow channel 11 supplies oxygen ions to the anode 2 facing the upper flow channel 12, and the lower wall supplies oxygen ions to the anode 2 facing the lower flow channel 12. Since it is necessary to supply, it can be said that it is inconvenient if the decomposition reaction illustrated in FIG. 16 does not occur. However, compared with the one-sided electrode structure isolated by the insulating partition sheet 13 of FIG. 16, the double-sided electrode structure shown in FIG. For this reason, air is also effective in reducing pressure loss.

  In the present embodiment, at least the anode-side channel 12 has the turn-up portion T, so that the channel length can be extended while being a small-area MEA or reaction portion, and has a double-sided electrode structure. , The reaction length required for detoxification (decomposition to very low concentration) can be shortened. Shortening the reaction length results in a reduction in pressure loss. For this reason, even if it is MEA of a smaller area, ammonia concentration can be reduced to a very low concentration level.

(Other embodiments)
The gas abatement apparatus of the present invention can be used for all the abatement reactions R1 to R7 shown in Table 1. In the first embodiment, the reaction R1 has been described.

  Regarding the ammonia detoxification, other reactions of R2 to R4 are possible. Of these, the reaction R4 is not a fuel cell reaction but an electrolysis reaction. However, the reaction R4 is the same as that of the first embodiment in terms of an electrochemical reaction, except for the difference between taking out and supplying electric power. There are also VOC (Volatile Organic Compounds) detoxification and NOx detoxification. For all these electrochemical reactions, it is possible to form a flow path having a folded portion and occupied by a metal porous metal plate. Moreover, it can also be set as a both-sides electrode flow path, especially having a folding | returning part and using said metal porous body. This makes it possible to obtain a gas abatement apparatus that can (1) be small, efficiently remove harmful gases to harmless levels, and (2) operate at low running costs.

(Example 1-Pressure loss and outlet concentration-)
Next, a change in concentration along the flow path when a predetermined concentration of ammonia-containing gas was allowed to flow through the flow path was calculated. This ammonia abatement apparatus removes ammonia-containing gas generated when a compound semiconductor GaN or the like is formed by an organic metal epitaxy method or the like. Although the ammonia concentration level that can be released into the atmosphere is restricted by laws and regulations, it is usually set to 1 ppm or less so that humans do not feel a bad odor as a lower concentration. In the simulation by calculation, the gas was a mixed gas of ammonia and hydrogen, and the ratio of ammonia and hydrogen was 1: 1. This mixed gas was treated by flowing 10 SLM. The ammonia decomposing apparatus 10 has a multi-layer laminated structure shown in FIG. 3 (a five-layer laminated structure having a single-side electrode flow path and having five flow paths. The MEA or the reaction part has a constant planar shape of 80 mm × 80 mm. Assuming that the ammonia concentration reached the anode is 100% decomposed, and 1/5 of 10 SLM is equally distributed to each channel. He said.

FIG. 18 shows the ammonia molarity that decreases as a function of the distance from the MEA inlet. Table 2 shows the pressure loss (pressure loss). What has one or more folding | turning parts corresponds to the example of this invention. According to Table 2 and FIG. 18, by providing one folding part, the ammonia concentration is increased from a molar ratio of 1 × 10 ⁻⁷ to 1 × 10 ^{−14 in a} state where the pressure loss is as low as about 2.2 kPa. It can be seen that it can be drastically reduced. As a result, it was possible to remove ammonia to a very low concentration by a small device by providing a folded portion using an MEA having a small size of 80 mm × 80 mm.

(Example 2-Influence of MEA size)
Similarly to Example 1, the influence of the MEA size on the ammonia concentration and pressure loss (pressure loss) was determined by calculation. The test specimens for calculation are as follows.
(Flow path structure): One-side electrode structure (MEA size): 20 mm □, 40 mm □, 80 mm □
(Current collector): Celmet (# 2) having a pore diameter of 1.9 mm and a specific surface area of 1000 m ² / m ³ was used. The thickness of the current collector was 3 mm, 6 mm, and two types.
(Number of cell stacks): The number of stacked MEAs was 5 layers.
(Ammonia-containing gas): A gas of NH ₃ : H ₂ = 1: 1 is flowed by 10 SLM.
Table 3 shows the pressure loss and ammonia concentration of each specimen.

Specimen No. with no folded part. 1, an ammonia molar ratio of 1 × 10 ⁻⁷ was obtained with an MEA size of 80 mm × 80 mm. On the other hand, by providing three folded portions, the test specimen No. As shown in FIG. 12, an ammonia molar ratio of 1 × 10 ⁻⁷ can be obtained at a pressure loss of 10 kPa or less with a very miniaturized apparatus having an MEA size of 20 mm × 20 mm.
Compound semiconductor atmospheric discharge of waste gas generated in the production is less than the pressure loss 10 kPa, and ammonia molar ratio less than 1 × 10 ^-5, it is necessary to satisfy. According to the above estimation, the prospect that the MEA size could be smaller than 20 mm × 20 mm was obtained using the one-side electrode structure and the flow path thickness of 3 mm.
Although the above is a case of the one-side electrode flow path, further downsizing can be realized by adopting a double-sided electrode structure.

  Although the embodiments of the present invention have been described above, 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.

  According to the gas abatement apparatus of the present invention, (1) it is small and efficient, it can remove harmful gas to a harmless level, and (2) it can be operated at a low running cost.

DESCRIPTION OF SYMBOLS 1 Ion conductive electrolyte (solid oxide electrolyte), 2 anode, 3 cathode, 3h space | gap, 10 ammonia decomposition | disassembly apparatus, 7 cathode collector, 7a cathode terminal, 7d electroconductive part, 7h pore, 8 anode collector, 8a Anode terminal, 13 insulating partition sheet, 15 channel wall, 21 metal particle chain, 21a core of metal particle chain (metal part), 21b oxide layer, 22 ion conductive ceramic of anode (SSZ, etc.), 31 metal particle Chain, 31a Core part of metal particle chain (metal part), 31b Oxidation layer, 32 Cathode ionic conductive ceramics (LSM, etc.), 33 Silver, 61 Ammonia-containing gas inlet, 62 outlet, 71 Air inlet, 72 outlet , C1-C7 channel, T turn-up section.

Claims (8)

An apparatus for removing chemical components in a gas by an electrochemical reaction,
A MEA (Membrane Electrode Assembly) composed of a pair of electrodes and an electrolyte sandwiched between the pair of electrodes,
Each of the paired electrodes is provided with a flow path for introducing a gas, and at least one folded portion is provided in a flow path of the electrode into which the gas containing at least the chemical component is introduced. ,
The gas abatement apparatus, wherein the flow path having the folded portion is occupied by a porous metal body having continuous pores.   The gas abatement apparatus according to claim 1, wherein the metal porous body is a metal plated body and has a porosity of 95% or more. Of the metal porous body, the pore size x (mm), when the specific surface area and ^{y (m 2 / m 3)} , and satisfies 400 ≦ (x-0.3) y , a, claim 1 Or the gas abatement apparatus of 2.   The MEAs are made into a set of two, and the pair of MEAs has both electrodes of the same polarity, with the electrodes having the same polarity facing each other, and the flow path having the folded portion sandwiched between the electrodes having the same polarity facing each other. The gas abatement apparatus according to claim 1, wherein the gas abatement apparatus is a flow path.   Each of the two MEAs includes a reverse-polar channel for introducing gas to an electrode having a polarity opposite to that of the electrode sandwiching the two-sided electrode channel, on the opposite side of the two-sided electrode channel. The gas abatement apparatus according to claim 4, wherein the area is equal to or larger than the larger cross-sectional area of the reverse flow path of the two MEAs.   A plurality of sets of gas abatement devices formed by the two MEAs are stacked, adjacent to each other, electrodes opposite in polarity to the electrodes sandwiching the both-side electrode channels are opposed to the opposite polarity channels. The gas abatement apparatus according to claim 5, wherein the gas abatement apparatus is sandwiched.   The gas abatement apparatus according to claim 6, wherein an insulating partition sheet is not provided between the plurality of stacked MEAs.   A gas containing ammonia is introduced into a flow path having the folded portion, and air is introduced into a flow path of an electrode opposite to the flow path. The gas abatement apparatus described.

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