JP5811494B2 - Gas cracker - Google Patents

Description

The present invention relates to an ammonia gas decomposition apparatus. More specifically, the present invention relates to an ammonia gas decomposing apparatus capable of decomposing a large amount of ammonia (NH3) gas .

For example, ammonia gas is discharged in a nitride manufacturing process in a compound semiconductor manufacturing apparatus or the like. Since ammonia gas adversely affects the human body and the environment, it must be released to the atmosphere after its concentration has been reduced to 25 ppm or less. Known methods for reducing the concentration of ammonia gas include a method for contact absorption by an aqueous solution such as sulfuric acid, a method for removal by introduction into a combustion furnace, a method for removal by contact with a dry detoxifying agent, and the like. Yes. Also known is a method in which ammonia gas is brought into contact with a catalyst at a high temperature and decomposed into N ₂ and H ₂ .

  In the conventional method in which ammonia gas is brought into contact with the catalyst at a high temperature, the catalyst filling part of the cylindrical container for decomposing ammonia gas is heated to the decomposition temperature. A structure in which a heater was embedded was employed.

JP-A-8-150320

  However, when a heating device is provided outside the cylindrical container, the heat transfer to the inside of the catalyst in which the gas flows is slow, so that when the gas flow rate increases, the gas cannot be heated sufficiently. . Further, a temperature difference inside the catalyst occurs, and unevenness in gas decomposition performance tends to occur. For this reason, it is difficult to construct a large-diameter container, and a gas decomposition apparatus capable of processing a large amount of gas cannot be constructed. Moreover, since the whole cylindrical container must be heated, thermal efficiency is also bad.

  When the heater is embedded in the porous catalyst, not only the heater but also an electrode portion for supplying power to the heater must be embedded in the porous catalyst through which the gas flows. For this reason, these electrodes etc. hinder the flow of the gas in the catalyst, and drift tends to occur. For this reason, it becomes impossible to make gas act on a catalyst uniformly.

  Furthermore, the flow rate of the gas flowing into the gas decomposition apparatus is not always constant. For this reason, when a heating device having a constant output is provided, the gas temperature increases when the gas flow rate is lower than the predetermined flow rate, while the gas temperature decreases when the gas flow rate exceeds the predetermined flow rate. Conventionally, the gas flow rate was adjusted by adjusting the heater output, but the heating device that heats from the outside cannot respond to the change in the flow rate because the heat transfer is slow, and the gas flowing in the container is efficient. Could not heat well.

The invention of the present application solves the above-described conventional problems, and does not hinder the flow of ammonia gas in the porous catalyst, can uniformly heat the flowing ammonia gas, and allows a large amount of ammonia gas to flow to improve efficiency. It is an object of the present invention to provide an ammonia gas decomposing apparatus that can be decomposed well and can heat ammonia gas to a constant temperature and act on a catalyst even when the flow rate fluctuates.

Ammonia gas decomposition apparatus according to the present invention, in a vessel gas is caused to flow, a ammonia gas decomposition apparatus constructed by filling a porous catalyst body, to the ammonia gas flow in the porous catalyst body In addition, a porous heating element having continuous pores is provided on the surface and / or inside of the porous catalyst body. The porous catalyst body is composed of an aggregate of spherical catalysts having a catalyst layer on the surface. Further, the porous heating element includes a skeleton having an exothermic outer shell and a hollow or / and conductive core, and a plurality of branches constituting the skeleton are gathered at a knot. A three-dimensional network structure that is integrally continuous is formed.

  In the present invention, the porous heating element is provided on the surface and / or inside of the porous catalyst body. That is, the porous heating element is provided integrally with the porous catalyst body inside the container that houses the porous catalyst body.

Since the heating element according to the present invention is a porous heating element having continuous pores, ammonia gas (hereinafter simply referred to as “gas”) can flow in the heating element. For this reason, even if it is provided on the surface or inside of the porous catalyst body, the heating element does not hinder gas flow. Therefore, there is no occurrence of gas drift or the like, and the gas can be made to act evenly on the porous catalyst body.

  The position where the porous heating element is provided is not particularly limited. For example, the porous heating element can be provided on the surface where the flowing gas flows into the porous catalyst body, and the gas can be heated immediately before coming into contact with the porous catalyst body. Moreover, it can prevent that the internal temperature of a porous catalyst body falls by providing so that it may embed | buy in the said porous catalyst body. As a result, the gas flowing in the porous catalyst body can be efficiently heated, and the temperature of the catalyst body can be prevented from decreasing even when a large flow rate is processed. In addition, even when the diameter of the cylindrical container is increased in order to process a large flow rate, the flowing gas can be heated uniformly to act on the catalyst.

It provided with a porous heating element of several, in which are configured to be able to selectively heated these heating elements.

  Since the heating element according to the present invention is a porous heating element, it does not hinder the gas flow even if it is provided in any part of the container. For this reason, it becomes possible to provide a plurality of porous heating elements and to heat the required heating elements in accordance with the flow velocity and temperature of the gas flowing through the heating elements.

  By adopting the above configuration, it is possible to easily cope with fluctuations in the amount of gas flow. It is also possible to dispose a porous heating element in a region where the temperature is likely to decrease and to uniformly heat the flowing gas.

On SL porous heating element, and forming into a plate shape that is provided along a plane perpendicular to the flow direction of the gas, so as to divide into a plurality of layers arranged to the catalyst in the flow direction of the gas can Rukoto provided on the.

  By adopting the above configuration, the gas flowing in the porous catalyst body can be heated in multiple stages, and the porous catalyst body can be heated to a constant temperature. In addition, since a required heating element can be energized among a plurality of porous heating elements, it is possible to respond quickly to fluctuations in flow rate.

  Furthermore, the function of adjusting the velocity of the flowing gas can be exhibited by providing the porous heating element and the porous catalyst body alternately. For example, if the pores of the porous catalyst body provided integrally are unevenly distributed, the flow path of the gas is bent to cause a drift, and the gas may not be brought into uniform contact with the porous catalyst body. Arise. By separating the porous catalyst body into a plurality of layers arranged in the gas flow direction and sandwiching a porous heating element between these layers, a porous catalyst body with nonuniform gas flow gaps is obtained. Even when employed, it is possible to prevent the gas from drifting and allow the gas to uniformly act on the porous catalyst body.

It can be configured with a porous heat-generating body provided in the vicinity of the central portion of the cross section perpendicular to the flow direction of the gas.

  In general, the flow velocity at the center of the cross section perpendicular to the gas flow direction is increased. For this reason, if the structure which heats the said cross section equally is employ | adopted, the gas temperature of a center part will fall. By providing the porous heating element in the vicinity of the center of the cross section perpendicular to the gas flow direction, the gas flowing through this portion can be heated, and the flowing gas can be heated uniformly.

It can be configured with a porous feeder for feeding the upper Symbol porous heating element. By adopting a porous body as a power feeding body that feeds power to the porous heating element, even if the power feeding body is provided in the gas flow path, the gas flow is not hindered. Therefore, the porous heating element can be installed in any part of the porous catalyst body. For example, it can be arranged in a part where the temperature is likely to decrease, and a large-sized ammonia gas decomposing apparatus capable of processing a large amount of gas can be configured.

  The material which comprises the porous catalyst body employ | adopted by this invention is not specifically limited. The material which comprises a catalyst body can be selected according to the kind of gas to decompose | disassemble. Further, the form of the catalyst body is not limited as long as the gas can flow at a required flow rate. For example, a catalyst body composed of an integrally molded porous body can be used.

Further, the porous catalyst body can be constituted by assembling a catalyst having a spherical or granular form. For example , the porous catalyst body can be constituted by assembling spherical catalysts having a catalyst layer on the surface. In this case, the porous catalyst body can be constituted by filling the container with a porous alumina sphere having a catalyst layer made of Ni—Cr or the like on the surface thereof by plating or the like. Further, in order not to increase the pressure loss when the gas flows, for example, it is preferable to employ alumina spheres having a diameter of 2 mm or more and to fill the porosity so as to be 25% to 80%.

When a catalyst body is formed by filling a spherical catalyst into a container, it is necessary to provide a holding means in order to hold the spherical catalyst in a predetermined shape. On SL porous heating element may be configured as the holding means.

  In the present invention, since the porous heating element can be provided on the surface of the porous catalyst body, a plate-like or sheet-like porous heating element is adopted, and the porous heating element is used as the holding means for the spherical catalyst or It can be used as a shape retaining means. As a result, it is not necessary to provide holding means formed from other members, and the number of parts can be reduced and the manufacturing cost can be reduced. In addition, when employ | adopting what has electroconductivity as the said porous catalyst body, it is preferable to provide an insulating layer between the said porous heat generating body and the said porous catalyst body. The said insulating layer can be formed according to the form of a porous catalyst body or a porous heat generating body. For example, when a porous catalyst body is formed by assembling spherical media, an insulating layer made of a spherical body having no electrical conductivity may be provided at the boundary surface between the porous catalyst body and the porous heating element. it can. In addition, an insulating layer can be provided by disposing a sheet-like member made of ceramic fiber or the like on the boundary surface.

To form the upper Symbol porous heating element in a plate shape, it can be configured with a circuit for supplying the current.

  When an electrode is provided at two points of an integral block or plate-like porous heating element and current is passed, the route through which the current flows is not specified, and the current flowing through the porous heating element is drifted, resulting in porous There is a risk that the entire heat generating element cannot be heated uniformly. By providing a circuit through which the current flows, it is possible to cause a current to flow through the entire porous heating element and to generate heat uniformly in the porous heating element.

  The method of providing the circuit and the form of the circuit are not particularly limited. For example, when a rectangular plate-like porous heating element is employed, a belt-like circuit can be formed by providing alternately parallel slits with a predetermined interval from opposite sides.

As the porous heating element , a porous heating element itself having a catalytic action can be adopted. As above Symbol porous heating element, integral with the outer shell having a heat generating resistance, comprising a skeleton and a core portion having a hollow and / or electrically conductive, a plurality of branches constituting the skeleton is assembled to the nub It is preferable to adopt a continuous three-dimensional network structure .

  Since the porous heating element is formed in a porous shape having continuous pores, gas can flow in the pores and can be efficiently heated.

In addition, since the porous heating element has a three-dimensional network structure, the porosity can be set extremely high. Thereby, the flow resistance of the gas in the pores is reduced, and a large amount of gas can be flowed and heated. In addition, a plurality of branch portions constituting the skeleton are formed so as to be integrated into a knot portion and continuous . For this reason, unlike a porous heating element configured by assembling fibrous heating elements, there is no contact resistance between adjacent fibers, and the electrical resistance in each part of the porous heating element changes greatly. There is no. Therefore, the current flow in the porous heating element is less unevenly distributed, and the entire porous heating element can be heated uniformly.

  The method for forming the skeleton is not particularly limited. For example, the skeleton can be formed by providing a plating layer or a metal coating layer on the surface of a three-dimensional network resin and eliminating the resin. By forming the outer shell of the skeleton from a metal plating layer or a metal coating layer, the thickness of the outer shell can be set very thin and uniform. Thereby, it becomes possible to form a porous heating element having a large porosity.

  The said core part is comprised from a hollow or / and electroconductive material according to a manufacturing method. For example, as described above, when the skeleton is formed by providing a plating layer on the surface of a three-dimensional network resin and erasing the resin, the portion where the resin has disappeared becomes hollow. In addition, when the surface of the three-dimensional network resin is coated with a conductive material to conduct the conductive treatment in order to provide the plated layer, the surface conductive layer made of the conductive material has a hollow core portion. It may remain on the inner peripheral surface. Further, when heat treatment or the like is performed after the plating process, the outer shell may shrink and the hollow portion may disappear.

  In the three-dimensional network structure in the porous heating element, a plurality of branches constituting the skeleton are gathered together at a knot and continuously integrated, and each of the branches gathered at one knot It is preferable that the outer shell has a substantially constant thickness. Since the current from each branch portion concentrates in the above-mentioned nodal portion, if the electric resistance of each branch portion gathering in one nodal portion is different, an excessive current flows in some branch portions around the nodule portion and the temperature May rise and the skeleton may melt or deteriorate. By setting the thickness of the outer shell of the branch part that gathers in one nodule part to be almost constant, it becomes possible to make the electrical resistance of each skeleton gathered in one nodule part almost constant, and in some skeletons Excessive current will not flow. Thereby, it becomes possible to prevent fusing and deterioration of the skeleton.

  Only the outer shells of the branches that gather at one node of the porous heating element need only be substantially constant, and it is not required that the thickness of the outer shell of the entire heating element be constant. For example, depending on the manufacturing method, the thickness of the outer shell may be different between the surface layer portion of the heating element and the inside. In this case, the thickness of the outer shell of each branch portion gathering at the nodal portion of the surface layer portion is different from the thickness of the outer shell of the branch portion gathering at the inner nodal portion. However, if the thickness of the outer wall of the branches gathered at each nodule is almost constant, an excessive current will not flow through some branches, and the skeleton near the nodule can be prevented from fusing. it can. Moreover, since the skeleton around the nodule portion has uniform strength, the strength as a porous body can be secured.

  When the outer shell is formed of a plating layer or the like, it is possible to form the outer shells of the branch portions gathering at one knot portion with a substantially constant thickness. Thereby, the dispersion | variation in the electrical resistance of the outer shell around a nodule part becomes small, and the whole region of a porous heat generating body can be heated uniformly.

  The material which comprises the said outer shell which is a heat generating body is not specifically limited. For example, it is preferable to form from an alloy containing 70 to 95% Ni and 5 to 30% Cr. By setting the blending amount within the above range, the porous heating element can be efficiently heated. Other components may be blended while maintaining the blending ratio of Ni and Cr. The Ni—Cr alloy has a catalytic action as well as a heating element. For this reason, it can also be utilized as a porous catalyst body.

  The porous heating element can be constituted by forming an alloy by diffusing Cr in a metal porous body mainly composed of Ni. It may be difficult to form a porous body having a required porosity directly from a Ni-Cr alloy. For example, it is difficult to directly form a Ni—Cr alloy plating layer.

  Therefore, first, a porous body can be formed from Ni, and a Ni—Cr alloy layer that functions as a heating element can be formed by diffusing Cr from the surface of Ni constituting the porous body.

  Since Ni is easily plated, the skeleton can be easily formed. Moreover, various metal porous bodies with different outer shell thicknesses and porosity can be easily configured. And by making this Ni porous body into a Cr alloy, various heating elements having required electrothermal characteristics can be configured.

  The method for forming the Ni porous body into a Cr alloy is not particularly limited. For example, the Ni porous body is made into a Ni-Cr alloy by heat-treating the Ni porous body in a mixed gas of a diffusion permeation component gas generated by heating the Cr source powder and a reducing dilution gas. Can do.

  In addition, the first outer shell and the second outer shell are formed by stacking a second outer shell made of Cr on the first outer shell made of Ni and performing a predetermined heat treatment. Can be diffused and alloyed to form the porous heating element.

The present gun invention are those according to the ammonia gas decomposition apparatus, the ammonia gas at room temperature and superficial linear velocity of the normal pressure (LV), to be able to flow in 0.1~200cm / sec On the other hand, it is preferable that the ammonia gas is made to flow at a flow rate corresponding to the flow rate at room temperature and normal pressure while heating to 450 to 1200 ° C. in the container . The superficial linear velocity (LV) means the velocity of the fluid flowing in the cylindrical container in which no packing or the like exists.

  In order to decompose the gas below the required concentration, it is necessary to heat the gas to 450 to 1200 ° C., which is the temperature at which the decomposition reaction occurs. Moreover, in order to ensure the time which contacts a catalyst, the inside of the container filled with the catalyst is at a flow rate corresponding to a flow rate at which the superficial linear velocity (LV) at room temperature and normal pressure is 0.1 to 200 cm / sec. It is preferable to flow ammonia gas. Furthermore, it can be made to flow at a flow rate corresponding to a flow rate at which the superficial linear velocity (LV) at room temperature and normal pressure is 0.1 to 20 cm / sec with the gas temperature heated to 600 to 900 ° C. It is desirable to configure as follows.

  With the ammonia gas flow rate set to the above value, the porosity, flow cross-sectional area, and heating temperature of the porous heating element so that the ammonia gas can be heated to the above temperature. Etc. are set. By setting the temperature and flow rate of ammonia gas as described above, the concentration of ammonia gas can be reduced to 25 ppm or less.

It is possible to provide an ammonia gas decomposing apparatus that can uniformly heat the flowing ammonia gas without disturbing the flow of the gas in the catalyst body and can efficiently decompose by flowing a large amount of ammonia gas. .

It is a longitudinal cross-sectional view which follows the axis line of the ammonia gas decomposition apparatus which concerns on 1st Embodiment. It is an expanded sectional view of the important section of a 1st embodiment. It is a longitudinal cross-sectional view which follows the axis line of the ammonia gas decomposition apparatus which concerns on 2nd Embodiment. It is sectional drawing which follows the IV-IV line in FIG. It is a top view of the heat generating body in FIG. It is an electron micrograph which shows an example of the structure of a porous heat generating body. It is a figure which shows typically the cross-sectional structure of the nodule part vicinity of the porous heat generating body shown in FIG. It is sectional drawing which follows the VIII-VIII line in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of an ammonia gas decomposition apparatus 100 (hereinafter referred to as “gas decomposition apparatus”) according to the first embodiment. The gas decomposition apparatus 100 includes a cylindrical container 1, porous heating elements 7, 8, 9, 10 and porous catalyst bodies 11, 12, 13 filled in the internal space of the container 1. ing.

  The container 1 is formed of a material such as metal, and includes a gas inlet 3, a gas outlet 4, the porous heating elements 7, 8, 9, 10 and the porous catalyst bodies 11, 12, 13. And a cylindrical space 1a to be filled. A heat insulating material 5 made of ceramic fiber or the like is provided on the inner peripheral portion of the side wall 2.

  The porous heating elements 7, 8, 9, and 10 according to this embodiment are formed in a disc or a column shape. On the other hand, the porous catalyst bodies 11, 12, and 13 are configured as an aggregate of spherical catalysts formed by providing a catalyst layer on the surface of a sphere formed of porous alumina. The porous heating elements 7, 8, 9, 10 and the porous catalyst bodies 11, 12, 13 are alternately stacked on the inner periphery of the heat insulating material 5 in a direction perpendicular to the gas flow direction. The integral porous body 6 is configured. In the present embodiment, there is provided a form in which the aggregate of the spherical catalysts is held between the porous heating elements 7, 8, 9, 10, and the porous heating elements 7, 8, 9, 10 are porous contacts. It is configured to function as a medium holding unit.

  Lead wires 7 a, 7 b, 8 a, 8 b, 9 a, 9 b, 10 a, 10 b for supplying power are drawn out from the side wall 2 of the container 1 on both sides of each porous heating element 7, 8, 9, 10. ing. Each lead wire is connected to a power source (not shown). In the present embodiment, a current is selectively passed through the lead wires of each porous heating element so that each porous heating element 7, 8, 9, 10 can be selectively heated.

  The porous heating elements 7, 8, 9, 10 and the porous catalyst bodies 11, 12, 13 are configured to have continuous pores, and pass the gas flowing in from the gas inlet 3 at a predetermined flow rate. The porosity is set to be possible.

  The porous heating elements 7, 8, 9, 10 are configured to generate heat at a temperature of at least 800 ° C., and the gas passing through the porous heating elements 7, 8, 9, 10 is given a predetermined temperature. It is comprised so that it can be heated.

  On the other hand, the porous catalyst bodies 11, 12, and 13 are set to have a performance capable of decomposing harmful components of the flowing gas to a predetermined concentration or less at the temperature and the gas flow rate.

  As shown in FIG. 2, the porous catalyst bodies 11, 12, and 13 are configured as an aggregate of spherical catalysts 20 in which a catalyst layer 20b is provided on the surface of a sphere 20a. In this embodiment, the spherical catalyst 20 in which the catalyst layer 20b is provided on the surface of the alumina sphere 20a having a diameter of 4 to 6 mm is employed. Thereby, the porosity of a porous catalyst body can be set to 40%-80%. Various materials can be adopted as the material constituting the sphere 20a as long as it has required heat resistance and the like. For example, ceramic spheres formed from porous alumina and metal spheres such as stainless steel can be employed. Further, the form of the catalyst body is not particularly limited, and it is also possible to adopt a form having an irregular granular form.

  The material constituting the catalyst layer 20b is not particularly limited. For example, a catalyst layer formed from Ni or a catalyst layer formed from a Ni—Cr alloy can be employed. In addition, a spherical catalyst having a catalyst layer formed of a different material can be used for each of the porous catalyst bodies 11, 12, and 13. In the present embodiment, the upper and lower porous catalyst bodies 11 and 13 are formed from an aggregate of spherical catalysts provided with a catalyst layer 20b formed from Ni—Cr, while the porous catalyst body 12 in the middle is formed from Ni. It consists of the aggregate | assembly of the spherical catalyst 20 provided with the formed catalyst layer 20b.

  On the other hand, the porous heating elements 7, 8, 9, 10 include a skeleton having an exothermic outer shell and a hollow or / and conductive core, and the skeleton is continuously continuous 3. What has a three-dimensional network structure is employable. For example, a porous heating element 401 having the form shown in FIGS. 6 to 8 can be employed.

  FIG. 6 is an electron micrograph showing the external structure of the porous heating element 401. The porous heating element 401 has a three-dimensional network structure having continuous pores 401b. As shown in FIG. 7, the three-dimensional network structure has a form in which triangular prism-like skeletons 410 are continuously connected in three dimensions, and a plurality of branch parts 412 constituting the skeleton are gathered at a nodal part 411. It has an integrally continuous form. Further, as shown in FIG. 8, each part of the skeleton 410 includes an outer shell 410a and a hollow core part 410b. In the embodiment shown in FIGS. 7 and 8, in the outer shell 410a, as described later, the plating layer 412a and the surface conductive layer 412b are integrally alloyed to function as a heating element. It is configured.

  Since the porous heating element 401 is formed in a porous shape having continuous pores 401b, gas can flow in the pores 401b and can be efficiently heated. In addition, the porous heating element 401 can have a very high porosity by adopting a three-dimensional network structure. For this reason, the flow resistance of the gas in the pores is low, and a large amount of gas can be flowed and heated.

  In addition, as shown in FIG. 7, the thickness t of the outer shell 410a of the branch portion 412 that gathers at one nodule portion 411 in the three-dimensional network structure is formed to be substantially constant. Since the thickness t of the outer shell of each branch portion gathering at one nodule portion 411 is substantially constant, the electrical resistance of each branch portion 412 gathering at one nodule portion is also substantially constant. Therefore, an excessive current does not flow through some branches gathered in one nodule. Thereby, it becomes possible to prevent fusing and deterioration of the skeleton.

  It should be noted that the thickness t of the outer shell 410a of the branch part 412 gathering at one node 411 of the porous heating element 401 may be substantially constant, and the thickness of the outer shell of the entire heating element is required to be constant. It is not something. For example, depending on the manufacturing method, the thickness of the outer shell may be different between the surface layer portion of the heating element and the inside. In this case, the thickness of the outer shell of each skeleton gathering at the nodal portion of the surface layer portion is different from the thickness of the outer shell of the skeleton gathering at the inner nodal portion. However, if the thickness of the outer shells of the branches gathering at one nodule is almost constant, an excessive current will not flow at least to some branches around the nodule, and the skeleton near the nodule Fusing can be prevented.

  The porous heating element 401 according to this embodiment is made of an alloy containing at least Ni and Cr. The blending amount of Ni and Cr can be set according to the required calorific value. For example, the outer shell 410 of the porous heating element 401 can be formed from an alloy containing 70 to 95% Ni and 5 to 30% Cr.

  The porous heating element 401 can be formed using various methods. For example, when the skeleton is formed by plating, the method includes a step of conducting a conductive treatment on a three-dimensional network resin, a step of metal plating the three-dimensional network resin, and a step of removing the three-dimensional network resin. Can be configured.

The form of the three-dimensional network resin, it is preferable to employ a resin foam. Although the raw material which comprises the said three-dimensional network resin is not specifically limited, It is preferable to employ | adopt what can be lose | disappeared by heating etc. after metal-plating. Moreover, in order to ensure workability and handling property, it is preferable to employ a flexible one. Tree fat foam may be a porous shape having continuous pores can be employed those known. For example, a foamed urethane resin, a foamed styrene resin, or the like can be used. There are no particular limitations on the pore shape, porosity, dimensions, and the like of the foamed resin, and they can be set as appropriate according to the application.

  The treatment for making the three-dimensional network resin conductive is performed in order to provide the metal plating layer constituting the skeleton on the surface of each pore, and particularly if the surface conductive layer 412b in FIG. 7 can be provided. There is no limit. For example, when nickel is used, an electroless plating process, a sputtering process, or the like can be employed. In addition, when adopting metals such as titanium and stainless steel, carbon black, graphite, etc., it is possible to employ a treatment of impregnating and applying the mixture obtained by adding a binder to these fine powders to the three-dimensional network resin. it can.

  The plating treatment is not particularly limited, and the treatment can be performed by a known plating method. For example, when nickel plating is employed, it is preferable to employ an electroplating method from the viewpoint of productivity, cost, and the like. A well-known or commercially available thing can be employ | adopted as a plating bath used for electroplating.

The thickness (weight per unit area) of the plating layer is not particularly limited. It can be set in consideration of the required porosity and strength. For example, it is possible to employ a unit weight of ^{100g / m 2 ~2000g / m 2} .

  After the plating layer is formed, a step of removing the three-dimensional network resin is performed. The step of removing the three-dimensional network resin may be performed by, for example, heat-treating the porous body provided with the plating layer at 600 ° C. to 800 ° C. in an oxidizing atmosphere such as air in a stainless muffle. Dimensional network resin can be removed by incineration.

  In order to obtain high heat generation performance, it is preferable to form the porous heating element from a Ni alloy having a large amount of Cr component. It is difficult to directly form the plating layer from an alloy material of Ni—Cr. For this reason, for example, it is possible to employ a technique in which a Ni plating layer and a Cr plating layer are separately formed and then alloyed. That is, a Ni plating layer is first formed on the three-dimensional network resin by the above-described method, and a Cr plating layer is laminated thereon. Thereafter, the three-dimensional network resin is removed and further heat-treated at a predetermined temperature, whereby the Cr plating layer and the Ni plating layer can be diffused and alloyed.

The thickness of the Cr plating layer (basis weight) also is not particularly limited, for example, can be set in a range of ^{10g / m 2 ~3000g / m 2} .

The Cr plating is performed by heat-treating the porous body in which the Cr plating layer and the Ni plating layer are laminated in a stainless steel muffle at 800 ° C. to 1000 ° C. in a reducing gas atmosphere such as CO or H _2. The Ni—Cr alloy layer can be formed by diffusing the layer and the Ni plating layer. Further, in an inert gas atmosphere such as N ₂ or Ar, an alloy layer can be formed from the Cr plating layer and the Ni plating layer by heating to 1000 ° C. to 1500 ° C. in a carbon muffle. When the surface conductive layer 412b shown in FIGS. 7 and 8 is provided by Ni, the surface conductive layer 412b is also Ni—Cr alloyed in the alloying step, and the whole becomes a heating element.

  By adopting the above process, it is possible to form a porous heating element with little variation in chromium concentration in the outer shell, high corrosion resistance and high heat generation characteristics. Further, since the outer shell is constituted by the plating layer, the thickness of the outer shell can be set almost uniformly in the porous body. For this reason, the dispersion | variation in the electrical resistance in a porous body decreases, and the whole porous body can be heated uniformly by supplying with electricity. In the above-described embodiment, the skeleton is formed by plating a three-dimensional network resin. However, the skeleton may be formed by coating a powder metal and then performing a heat treatment. In this case, a Ni—Cr alloy can be formed at a time by coating a powder containing Ni powder and Cr powder.

  As shown in FIG.7 and FIG.8, although the said core part which concerns on this embodiment is formed in hollow shape, it is not limited to this. That is, in the above-described embodiment, the surface conductive layer 412b formed of Ni is integrated with the outer shell because it is Cr alloyed. However, when the surface conductive layer is formed of another conductive material, the core It may remain as a part. For example, when the surface conductive layer is formed of titanium, carbon, or the like, and the skeleton is formed by Ni plating and then Cr alloyed, the surface conductive layer 412b remains as a core without being alloyed. Become. Further, in the heat treatment step of forming the Ni plating layer into a Cr alloy, the outer shell may shrink and the hollow core portion may disappear.

  In the present embodiment, the porous heating elements 7, 8, 9, and 10 and the porous catalyst bodies 11, 12, and 13 have conductivity, and when in direct contact with the porous heating elements 7, 8, 9, and 10, An electric current flows between the porous catalyst bodies 11, 12 and 13, and the porous heating elements 7, 8, 9, and 10 cannot be heated at a required temperature. In order to avoid the inconvenience, as shown in FIG. 2, alumina in which a conductive catalyst layer is not provided between the porous heating elements 7, 8, 9, 10 and the porous catalyst bodies 10, 11, 12. An insulating layer 30 composed of a sphere 30a is provided.

  The results of Examples 1 to 3 in which ammonia gases having different concentrations are flowed in the gas decomposition apparatus 100 having the above configuration are shown below. In the present example, the porous heating element having the above-described configuration and having a porosity of 96% was used. In addition, the porous catalyst body having the above-described configuration and having a porosity set to 60% was used.

[Example 1]
In the gas decomposing apparatus shown in FIG. 1, a gas having an ammonia concentration of 10% is supplied in a state where a current is passed through the lead wires 7 a and 7 b of the porous heating element 7 provided at the upper portion and the porous heating element 7 is held at 800 ° C. Was introduced into the container 1 from the gas inlet 3 and the gas flow rate in the gas decomposition apparatus was set to 5 cm / sec to decompose the gas.
In Example 1, the ammonia concentration of the gas discharged from the gas discharge port 4 was 25 ppm or less.

[Example 2]
A current is passed through the lead wires 7a and 7b of the porous heating element 7 provided in the upper part and the lead wires 8a and 8b of the porous heating element 8 provided in the middle part, so that the porous heating element 7 and the porous heating element 8 are provided. While maintaining the temperature at 800 ° C., a gas having an ammonia concentration of 20% is introduced into the container 1 from the gas inlet 3 and the gas flow rate in the gas decomposition apparatus is set to 10 cm / sec to decompose the gas. Went.
In Example 2, the ammonia concentration of the gas discharged from the gas discharge port 4 was 25 ppm or less.

Example 3
Lead wires 7a, 7b, 8a, 8b, 9a, 9b, 10a. Of all porous heating elements 7, 8, 9, 10. An electric current is supplied to 10b, and a gas having an ammonia concentration of 30% is introduced into the container 1 from the gas inlet 3 in a state where all the heating elements 7, 8, 9, 10 are held at 800, The gas was decomposed at a gas flow rate of 20 cm / sec.
In Example 3, the ammonia concentration of the gas discharged from the gas discharge port 4 was 25 ppm or less.

  As is clear from each example, the heating elements 7, 8, 9, and 10 are selectively heated according to the concentration and flow rate of the ammonia gas, thereby decomposing the ammonia gas below the required concentration. Can do.

  3 and 4 show a second embodiment of the present invention.

  In the gas decomposition apparatus 200 according to the second embodiment, plate-like porous heating elements 207 and 208 are provided on the upper and lower ends in the axial direction of the porous catalyst body 212 so as to sandwich the porous catalyst body 212, and the porous A cylindrical porous heating element 209 is embedded in the central portion of the porous catalyst body 212. In the second embodiment, the configuration of the porous catalyst body 212 and the configuration of the porous heating elements 207, 208, and 209 are the same as those in the first embodiment, and a description thereof will be omitted.

  The porous heating element 209 has a cylindrical shaft embedded in the direction in which the gas flows, and has a porous structure similar to that of the porous heating element 209 and is made of nickel. 209b and lead wires 210a and 210b are configured to be able to supply power.

  In the present embodiment, the porous heating element 209 is disposed in the central portion of the porous catalyst body 212 where the gas temperature is likely to decrease, particularly in the vicinity of the central portion of the cross section perpendicular to the gas flow direction. With this configuration, it is possible to heat the central portion where the gas flow rate is fast and the temperature is likely to decrease, and the gas flowing in the porous catalyst body can be heated uniformly.

  Moreover, since not only the porous heating element 209 but also the power feeding bodies 209a and 209b are composed of the same porous body as the porous heating element, the flow of gas in the porous catalyst body is not hindered. . For this reason, it becomes possible to make gas decompose into contact with the catalyst body evenly.

  In the present embodiment, the cylindrical porous heating element 209 is employed, but the form of the porous heating element may be set so that the gas can be heated uniformly according to the form of the container and the like. Although not shown, an insulating layer made of a breathable sheet made of ceramic fibers or the like is provided on the surfaces of the porous heating element and the porous conductor.

  As shown in FIG. 5, the porous heating elements 207 and 208 provided on the upper and lower end surfaces of the porous catalyst body 212 are entirely formed in a disk shape corresponding to the internal space of the cylindrical container 201, Slits 308, 309, 310, 311, 312, 313, and 314 extending alternately from opposing edges are provided. In addition, power supply bodies 316a and 316b are connected to the end portions of the band-shaped region defined by the slits, and lead wires 207a and 207b are extended from the power supply bodies 316a and 316b to the outside of the container 201, A power source 320 is connected.

  By providing the slits 308, 309, 310, 311, 312, 313, and 314, a band-like circuit having a constant width is formed in the porous heating element 207. For this reason, an electric current can be sent over the whole area of the disk-shaped porous heating elements 207 and 208, and it can be heated uniformly.

  By adopting the above configuration, even when a large flow rate of gas flows in the porous catalyst, it can be heated uniformly and brought into contact with the catalyst, and the flowing gas can be efficiently decomposed.

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

  A gas decomposing apparatus that can be decomposed efficiently by flowing a large amount of gas while being heated and that can be decomposed by heating the gas to a constant temperature even if the flow rate of the gas fluctuates can be configured.

DESCRIPTION OF SYMBOLS 1 Container 7 Porous heating element 8 Porous heating element 9 Porous heating element 10 Porous heating element 11 Porous catalyst body 12 Porous catalyst body 13 Porous catalyst body 100 Gas decomposition apparatus

Claims (8)

In a vessel ammonia gas is caused to flow, a ammonia gas decomposition apparatus constructed by filling a porous catalyst body,
The ammonia gas is caused to flow in the porous catalyst body,
A porous heating element having continuous pores on the surface and / or inside of the porous catalyst body is provided ,
The porous catalyst body is composed of an aggregate of spherical catalysts having a catalyst layer on the surface,
The porous heating element includes a skeleton having an exothermic outer shell and a hollow or / and conductive core part, and a plurality of branches constituting the skeleton are assembled into a knot and integrated. An ammonia gas decomposing apparatus having a continuous three-dimensional network structure . The ammonia gas decomposing apparatus according to claim 1, wherein a plurality of the porous heating elements are provided, and the heating elements are configured to selectively generate heat. The porous heating element is formed in a plate shape provided along a plane orthogonal to the gas flow direction, and divides the catalyst body into a plurality of layers arranged in the gas flow direction. The ammonia gas decomposition apparatus according to claim 1 or 2 , which is provided as described above. The ammonia gas decomposing apparatus according to any one of claims 1 to 3, further comprising a porous heating element provided in the vicinity of a central portion of a cross section perpendicular to the gas flow direction. The ammonia gas decomposing apparatus according to any one of claims 1 to 4, further comprising a porous power supply that supplies power to the porous heating element. The ammonia gas decomposition apparatus according to any one of claims 1 to 5, wherein the porous heating element constitutes a holding means for holding the spherical catalyst. The ammonia gas decomposition apparatus according to any one of claims 1 to 6 , wherein the porous heating element is formed in a plate shape and includes a circuit through which a current flows. On SL ammonia gas at room temperature and superficial linear velocity of the normal pressure, with constituted to be able to flow in 0.1~200cm / sec, the ammonia gas in the vessel, 450-1200 The ammonia gas decomposing apparatus according to any one of claims 1 to 7, wherein the ammonia gas decomposing apparatus is configured to flow at a flow rate corresponding to the flow rate at room temperature and normal pressure while being heated to ° C.

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