JPS6130819B2 - - Google Patents

Description

[Detailed description of the invention]

Due to the increase in fossil fuel consumption and the enlargement of various plants, carbon monoxide, hydrocarbon compounds,
The content of harmful gases such as nitrogen oxides, sulfur oxides, and ammonia has increased, creating photochemical smog and oxidants, and affecting the human body, which has become a major social problem. For this reason, legal regulation values have been established for the emissions of these harmful gases, and efforts are being made to reduce emissions by improving combustion methods.Sulfur oxides have been legally regulated by applying wet-method desulfurization equipment. The desulfurization technology can be said to have been completed as it has become possible to fully satisfy the values. On the other hand, various methods have been proposed for the removal or reduction of other harmful gases, but the method of detoxifying and removing them using a dry method using a catalyst is a relatively simple process, has a large processing capacity, and requires post-treatment. Because it is an unnecessary method, it has been intensively researched and in some cases has been put into practical use. The present invention relates to a method for producing a catalyst used in detoxifying and removing this type of harmful gas,
It is particularly suitable for treating exhaust gases containing dust and sulfur oxides from coal-fired boilers, heavy oil-fired boilers, and the like. However, the present invention provides a catalyst that contains almost no dust or sulfur oxides and can be applied to the treatment of exhaust gas emitted from mobile sources such as automobiles. The catalyst of the present invention is particularly effective when applied as an oxidation catalyst for carbon monoxide and hydrocarbon compounds, as a reduction catalyst for nitrogen oxides, and as an oxidation catalyst for ammonia through reaction with oxygen or nitrogen oxides. However, here we will explain the nitrogen oxide reduction catalyst. Methods for removing nitrogen oxides (hereinafter abbreviated as NOx) from exhaust gas include adsorption methods, oxidation absorption methods, solidification collection methods, and catalytic reduction methods, but the catalytic reduction method, which does not require post-treatment, is the economical technology. It is also advantageous,
The selective catalytic reduction method, which is not affected by the oxygen concentration in the exhaust gas, is economically advantageous and is being intensively researched in various fields. Traditionally, alumina, titania, zirconia, silica,
Porous refractory materials such as diatomaceous earth and zeolite calcium sulfate have been used alone or in combination, but both are expensive because they are used in granulated form. Furthermore, for clean gas that does not contain any dust or SOx, it is possible to granulate the carrier mentioned above into any shape such as spherical or cylindrical, and bring the exhaust gas into contact with the catalyst layer perpendicularly. In order to develop exhaust gas treatment technology that contains a large amount of dust, such as boiler exhaust gas fueled by coal, garbage incinerators, and coke oven exhaust gas, it is necessary to take measures to prevent dust from accumulating in the catalyst layer. For this purpose, methods are being considered, such as making the catalyst shape cylindrical or honeycomb-like to make it easier for the dust to pass through, and moving the granular catalyst to scatter the adhering dust. A method of preventing dust adhesion by flowing is also promising, and the present inventors are also working on the development of a catalyst that can be applied to this method. One of the optimal shapes for this method is a plate-like structure, and it has been proposed to use a nonmetallic fireproof board made of inorganic material as a catalyst as a material that can be manufactured at low cost, is lightweight, and has considerable strength. However, when making this type of molded plate larger, it needs to have enough strength to withstand use and be flat overall without warping, so the thickness of the plate must be increased as the size increases. A satisfactory catalyst base material cannot be obtained. For example, for a 1m square plate, the maximum thickness is 5mm. In order to create a dust-free type, it is common to set the plate spacing to 5 mm or more, so when a plate-like structure is used, the catalyst packing becomes larger, and there are restrictions on the installation location or when reducing the cost of the denitrification equipment. In order to do this, it will be necessary to make it more compact, and users are starting to make requests for this type of technology as well. Therefore, the present inventors have also proceeded with the development of metal-based catalysts in order to reduce the thickness of plate-shaped catalysts, and have proposed various catalytic methods. The metal base material itself has a high specific gravity, but the plate thickness is 0.6 ~
Even 1.0mm is strong enough to withstand use, so if the capacity is the same as a structure made of non-metallic fireproof boards made of inorganic substances, the number of catalysts filled will be 1.5 to 2.0 times, so the same performance can be achieved. There is an advantage that the size can be reduced by about 50% to 70% compared to the conventional case. Therefore, there is a method of activating the metal itself (Japanese Patent Application No. 52-2782), and a method of adhering and supporting a catalyst on a foam such as a sponge metal (Japanese Patent Application No. 52-2782).
10111), and a method in which the surface of a corrosion-resistant stainless steel material is roughened by sandblasting or the like and a slurry material containing a catalyst component is applied to support the catalyst. However, although the activation treatment of the metal itself has initial activity, its performance deteriorates when used in exhaust gas containing SOx, making it difficult to put it into practical use. Although the use of sponge metal is good in terms of performance, it is difficult to apply because metal materials are expensive. Furthermore, since the adhesion layer of the coating-adhesive type using stainless steel material is thin, when used as a structure in actual gas, there is a concern that the catalyst component may peel off due to surrounding vibrations, so the thickness of the adhesion layer must be increased. There is. However, if the catalyst component is deposited thickly, it may peel off from the base material, so the limit is 50 to 70μ. Therefore, the present inventors have developed a metal composite material that uses an inexpensive metal material (for example, SPCC) as a base material, which has insufficient corrosion resistance, and has been imparted with corrosion resistance and has a roughened base material surface, thereby making it possible to create an extremely excellent catalyst. I discovered that. In general, metal materials with poor corrosion resistance such as SPCC are protected by enameling to make the surface layer glassy. However, since there is no grip, it does not adhere firmly. Therefore, in order to increase the surface roughness after enamel processing, about 50% of silica sand powder with a particle size of 20 to 100 mesh is added to the lower glaze for enamel, and even when the glaze is uniformly mixed and dried and fired, the silica sand powder is Since the surface layer is covered with glass, the surface roughness appears to be increased, but since the aforementioned ceramic material does not adhere well to the base material, it is as satisfactory as enameling with only underglaze. You can't get what you want. Therefore, the present inventors added clay, silica powder, borax, and glaze stopper to the frit in order to improve the adhesion with the ceramic material after enamel treatment.
After the metal material is immersed in a glaze prepared by adding and mixing water, fine inorganic refractory powder is uniformly and densely sprinkled on the surface layer that comes into contact with the glaze before the water is removed, then dried and fired. It has been discovered that the surface roughness of metal materials can be increased by bonding the inorganic refractory fine powder. Originally, enameling was applied to inexpensive iron plates to prevent rust and give a beautiful finished surface.
The main focus is on providing alkali resistance while providing a rough finished surface. The metal material is not limited as long as it can be enamel-processed, but taking into account its low cost, ordinary mild steel plates or enameling steel plates with extremely low carbon content are suitable. The underglaze is not limited as long as it becomes glassy when fired, but it is preferable that it be acid resistant and alkali resistant. The glaze is made of refractory raw materials such as silica stone, silica sand, and feldspar, borax, boric acid, soda ash, chili saltpeter, potassium saltpetre, lithium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, lead tan, lead oxide, zinc oxide, etc. molten raw materials, fluorite, cryolite, sodium silicate, tin oxide, antimony oxide,
Milky white raw materials such as antimony metal, sodium antimonate, titanium oxide, zirconium oxide, zirconium silicate, arsenite, cerium oxide, cobalt oxide, chromium oxide, nickel oxide, manganese dioxide, copper oxide, iron oxide, potassium dichromate ，
Coloring materials and adhesives such as cadmium sulfide, metallic selenium, and lead chromate, floating agents such as clay bentonite, and stoppers such as borax, soda ash, ammonium carbonate, magnesium carbonate, barium chloride, lime water, and magnesium sulfate, etc. The required amount of mixed and melted frit is finely pulverized and, if necessary, milled grains are added thereto and suspended in water. The glazing method may be spray, drizzle, drizzle, etc. Drying should be done until the moisture in the glaze is removed, and firing should be done at 700℃ to 1000℃ for 2 to 3 minutes. It is enameled. Furthermore, the present invention is not limited to uniformly sprinkling fine powder onto the lower glaze; the purpose can also be achieved by uniformly sprinkling fine powder onto the upper glaze; however, in terms of cost, It is cheaper to process. The inorganic refractory fine powder sprinkled on the glazed metal material can be crushed rock products, various cements, fly ash, various aggregates, gypsum, lime, magnesia, etc.
Any material can be used, such as various types of refractory bricks and clay foundry sand, but silica sand powder is usually used. Further, the particle size is not limited depending on the desired roughness, but particles of about 20 to 100 mesh are used. Instead of the above-mentioned enamel treatment, using alumina, silica, or alumina-silica-based paints that are heat resistant up to 700 to 800 degrees Celsius, or heat-resistant paints containing these as their main ingredients, will show the same effect as the enamel treatment. It is something. That is, the object of the present invention is achieved by applying a heat-resistant paint using a brush, roll method, or dipping method, and before the paint is dry, evenly scattering inorganic refractory fine powder similar to that used in the enamel treatment and drying and baking. A metal material with a roughened surface is obtained. At this time, the method of adding and mixing inorganic fire-resistant fine powder to heat-resistant paint and applying it is limited by the amount of fine powder added due to viscosity. As explained above, there are disadvantages such as the surface layer of the fine powder is coated with the paint, which reduces its effectiveness by half, and the inorganic refractory fine powder is not evenly distributed. It is preferable to add. The metal composite material with a rough surface obtained by the method described above can be made into a metal-based catalyst with a thick 150 to 200μ of catalytic component supported by adhering and supporting the catalytic component on the surface. became possible. In other words, by supporting porous refractories such as alumina, silica, titania, zirconia, and calcium sulfate with noble metal elements such as platinum, palladium, rhodium, and ruthenium, either alone or in combination, carbon monoxide, which is emitted from automobiles, etc. Oxidation catalyst that removes hydrocarbon compounds and nitrogen oxides,
Reduction catalyst or three-way catalyst (reduces NOx, converts CO and
It can be provided as a catalyst that oxidizes and simultaneously removes HC.
Oxides or sulfate compounds of base metal elements such as copper, vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, and tungsten are used alone or in combination with zirconia, etc. to suppress SO ₂ oxidation and stabilize the catalyst. It is used as a NOx removal catalyst that uses ammonia as a reducing agent to which small amounts of oxides such as tin, zinc, cerium, lanthanum, and barium are added to reduce the amount of oxidation, or as an ammonia decomposition catalyst that uses NOx and oxygen in exhaust gas. The method of adhering and supporting the catalyst component on the metal composite material subjected to the above-mentioned pretreatment is not particularly limited, and a slurry solution in which the catalyst activity imparting component is added to porous refractory powder by a kneading method or an impregnation method is used. It can be obtained by coating the metal composite material and then drying it or, if necessary, firing it. By using molded products such as pre-notching the metal base material, it is possible to easily create a catalyst structure with a certain gap, which can be used to remove large amounts of dust and sulfur oxides from heavy oil-fired boilers, coal-fired boilers, etc. The present invention provides a method for producing a catalyst that is extremely effective in removing harmful components contained in exhaust gas and rendering it harmless. The present invention will be specifically explained below using Examples. [Example 1] After chemical pretreatment such as degreasing, pickling, nickel treatment, and neutralization of a cold rolled steel plate (SPCC) with a thickness of 1 mm as a metal material, SiO ₂ 45.2%,
Al ² O ₃ 8.5%, B ₂ O ₃ 17.1%, CaO 3.0%, K ₂ O 4.1
%, Na ₂ O 15.0%, NiO 1.2%, CoO 2.9%,
Fritz with a composition of MnO2.5% and ZnO0.5%
Add 5 parts of viscosity, 15 parts of silica powder, 0.5 parts of borax, 0.3 parts of sodium nitrite, and 50 parts of water to 100 parts, and immerse it in a uniformly mixed glaze.
Metal composite material 1 was obtained by scattering ~50 meshes of silica powder without any gaps, thoroughly drying it, and then firing it at 820°C for 2 minutes. Next, 8 parts of vanadium pentoxide, 3 parts of tungsten oxide, and 150 parts of water were added to 100 parts of anatase-type titanium oxide powder, stirred thoroughly to make a uniform slurry, and then applied to metal composite material 1 at 150°C. So 5
Catalyst 1 was obtained by drying for hours. The amount of catalyst deposited at this time was on average 150μ when converted into film thickness. [Example 2] A heat-resistant paint (Pyrosin, manufactured by Oshima Kogyo) was applied to an SPCC substrate with a thickness of 1 mm, and before the paint dried, silica powder with a particle size of 30 to 50 mesh was sprinkled without any gaps, and thoroughly coated. After drying, a baking treatment was performed at 200° C. for 1 hour to obtain a metal composite material 2. Next, catalyst 2 was obtained in the same manner using the slurry of Example 1. The amount of catalyst deposited at this time was on average 180μ when converted into film thickness. [Example 3] Using an SPCC steel plate (plate thickness 0.8 mm notch, flat type) as an air heater element,
Catalyzed in the same manner as in Example 1, 500 mm x 500 mm x
Four structures of 1000mm (catalyst spacing 6mm) are connected in series.
Placed in the exhaust gas flue of a heavy oil-fired boiler, with a gas volume of 2000N.
^m3 /H, gas temperature 330-380℃, _NH3 /NOx=1.0
We conducted a 2000 hour durability test and achieved a denitrification rate of 95-98%. [Example 4] Table 1 shows the catalyst components to be attached to the metal composite material 1.
Catalysts 3 to 15 were obtained by selecting the catalysts shown in .

[Table] Shows the content of fireworks.
Catalysts 3, 13, and 14 are used as oxidation catalysts for carbon monoxide and hydrocarbon compounds, and catalyst 4 is used as a catalyst for purifying NOx discharged from internal combustion engines such as automobiles.
No. 15 was tested on automobile exhaust gas as a three-way catalyst that simultaneously reduces these three components, and good performance was obtained. Of course, it is difficult to achieve the same performance as conventional products because the amount of catalyst is smaller than the granular catalysts and honeycomb catalysts used as conventional exhaust gas purification catalysts. By using the catalyst of the present invention, purification is achieved by approximately 20 to 30%, which has the advantage of reducing the amount of conventional catalysts used. Catalysts 5 to 12 are used as denitrification catalysts using ammonia as a reducing agent, and a performance evaluation test was conducted using the exhaust gas source shown in Example 3, and the results shown in Table 2 were obtained. The test catalyst at this time was 50×200×
10 sheets/row of 1 mm thick sheets were arranged at 7 mm intervals, and these were arranged in 3 steps. And gas amount 10N
m ³ /H, gas temperature 350°C, NH ₃ /NOx = 1.0 cm ² test was conducted.

[Table] As mentioned above, the catalyst of the present invention is a catalytic technology based on a very unique manufacturing method using metal as a base material, and has a wide range of applications, so it provides a highly practical catalyst manufacturing method in various fields. be.

Claims (1)

[Claims] 1. A metal composite material or metal surface obtained by applying a metal enamel glaze to a metal surface, and before the glaze dries, uniformly scattering a fine inorganic refractory powder, followed by drying and firing. A metal composite material with a catalyst component supported on its surface layer is obtained by applying a heat-resistant paint to the surface of the metal composite material, and before the paint dries, uniformly scattering a fire-resistant fine powder made of an inorganic material, followed by drying and firing. A method for producing a catalyst.