JPS6234586Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a denitrification catalyst device, and its purpose is to provide a denitrification catalyst that can efficiently proceed with gas exchange reactions, exhibits high activity even under high temperatures, has excellent wear resistance, and is resistant to peeling of catalyst components. This invention relates to a catalyst device. For selective reduction of exhaust gas using NH ₃ , TiO ₂ -V ₂ O ₅ based pellet catalysts have been known as highly active denitrification reaction catalysts with excellent SOx resistance. However, this type of catalyst has the drawback that its activity levels off at reaction temperatures of 350°C or higher.
This is thought to be caused by a decrease in NH ₃ adsorption and a decrease in the catalyst effectiveness coefficient. An effective measure for the former is to improve performance by adding other elements, and a possible measure for the latter is to change the form of the catalyst. However, changing the catalyst form has various problems. The catalyst effectiveness coefficient is expressed as a function of the true reaction rate constant, average pore diameter, catalyst layer thickness, etc.
The TiO ₂ −V ₂ O ₅ catalyst has the characteristics of a large true reaction rate constant and a small average pore diameter. Therefore, the effective coefficient of the TiO ₂ -V ₂ O ₅ catalyst tends to be small, and this tendency is particularly noticeable in the high temperature range where the reaction rate is extremely high. Therefore, in order to increase the catalytic effectiveness coefficient, it may be possible to reduce the thickness of the catalyst layer, but in this case, the amount of contact per unit area will decrease, and the activity will decrease. Therefore, in order to increase the catalytic effectiveness coefficient, it is effective to arrange catalyst components made of extremely thin layers or fine powder at appropriate distances. However, since such a catalyst is extremely porous, it has poor pressure resistance and abrasion resistance. On the other hand, when the catalyst is in the form of pellets, only the surface active layer portion of the pellet acts effectively as a catalyst, and the center portion, which occupies most of the rest, cannot contribute to the reaction. As a result, the weight of the catalyst inevitably increases, and the heat capacity also increases correspondingly, and in plants where operations are frequently started and stopped, the denitrification equipment cannot follow this increase. Furthermore, the presence of dust in the exhaust smoke not only tends to cause dust clogging in the pellet layer, but also increases pressure loss, making it necessary to install a large exhaust fan. In order to solve the above-mentioned problems with pellet catalysts, plate-type or honeycomb-type catalysts have been viewed as promising. However, this type of catalyst
If it is formed only from TiO ₂ −V ₂ O ₅ based components, these components are ceramics and are therefore fragile.
Poor impact resistance makes it difficult to manufacture large-sized catalysts, and porous ceramics are not practical because they are easily powdered by dust. Therefore, in order to increase the strength of the catalyst, it may be possible to obtain a catalyst by forming a plate or honeycomb-structured skeleton using a metal material and coating the surface with catalyst components. There is a difficulty in maintaining a large bonding force with the catalyst component, and peeling is likely to occur due to the difference in thermal expansion between the two, vibration, etc. In order to improve this point, if the skeleton is composed of a wire mesh, there is less risk of the catalyst component peeling off than in the case of a plate skeleton, but the difference in thermal expansion between the two can cause cracks in the catalyst component layer. When used for a long period of time, catalyst performance deteriorates due to so-called chipping. Furthermore, since the catalyst component layer is constantly in contact with exhaust gas containing dust, the hard dust directly abrades the catalyst layer, accelerating its performance deterioration. Therefore, in order to improve the strength of the catalyst component layer, attempts have been made to increase the density of the component layer or increase the amount of binder, but this leads to filling the pores necessary for the catalytic reaction and increases the activity. causing a decline. The present invention has been made in view of the above points. The present invention is characterized in that the denitrification catalyst is supported on a catalyst carrier made of wire mesh woven with long glass fiber bundles, and the catalyst is formed in a honeycomb shape so that the flow of exhaust gas and the catalyst surface are parallel to each other. Examples thereof will be described below. 1 to 4, the wire mesh 1 is made up of relatively thick needle wires 1A, 1B arranged vertically and horizontally at equal pitches. The fabric is woven in such a manner that a single vertical needle line 1A can alternately run over one side of a large number of horizontal needle lines 1B, and a single horizontal needle line 1B can alternately run over one side of a large number of vertical needle lines 1A. A glass fiber bundle 2, which is a bundle of small-diameter non-alkali glass long fibers 2A, is woven through the wire mesh 1 between a large number of vertical needle lines 1A. These glass fiber bundles 2 take a form such that they can alternately ride on one side of a large number of horizontal needle lines 1B. Such a skeleton structure is used as the catalyst carrier 3. The catalyst carrier 3 is formed into a plate shape or a mountain shape, and after a powdered catalyst component is applied and fired, the plate catalyst and the mountain catalyst are alternately formed into a honeycomb shape as shown in FIG. Reaction tube 5
The catalytic converter is disposed in a smoke exhaust passage 6 surrounded by the inside so that the smoke exhaust direction and the catalyst surface are parallel to each other. Next, the experimental results will be explained. A catalyst carrier made of SUS, made of a wire mesh with a wire diameter of 1 mm and a mesh size of 5 mm x 5 mm, and a bundle of non-alkali glass long fibers with a thickness of about 10 μm woven into it, is coated with powdered titanium along with a binder to coat the catalyst. Manufactured. In this case, commercially available powdered titanium for catalysts is used as a catalyst component by crushing it into 100 mesh or less.
In addition, as a binder, it is 1/1/1 by weight of powdered titania.
About 10% of NH ₃ VO ₃ and about 1/2 of a silica gel solution by weight were used, and a slurry of the mixture was applied to a surface-activated alkali-free glass long fiber bundle using a brush or a scraper. The amount of application is
It was ^about 150g/m2. Next, this was dried at about 100°C and then fired at 400°C for about 1 hour. The plate-shaped catalysts 4A and mountain-shaped catalysts 4B thus obtained are arranged alternately to form a honeycomb structure as shown in FIG. It was placed so that it was parallel to the flow direction of the flue gas.

[Table] Next, the prepared exhaust gas for the test shown in the table above was passed through a quartz flow-through type reaction tube at a flow rate of AV20, and the denitrification rate was determined from the difference in NO concentration at the inlet and outlet of the reaction tube.
This was compared with that of a conventional pellet catalyst.
Comparison results at various reaction temperatures are shown in FIG. In FIG. 5, a shows the performance curve of the catalyst using the carrier according to the present invention, and b shows the performance curve of the conventional pellet catalyst. As is clear from FIG. 5, the catalyst using the carrier according to the present invention exhibits higher activity at each temperature than the conventional catalyst, and the decrease in the effective coefficient is small. The reason why the catalyst used in the device of the present invention exhibits a high effective coefficient is that the catalyst component (catalyst effective component) is contained in the thin long glass fibers 2A, as shown in FIG.
This seems to be due to the fact that even though the thin long glass fibers 2A are woven into the wire mesh 1 in the form of a bundle, the holes 8 are reliably secured between them. That is, this ensures a structure in which the gas exchange reaction proceeds efficiently over a long period of time. Further, as shown in the above experimental example, the catalyst component 7 is ceramic, and therefore, the catalyst component 7 is made of ceramic.
The bond between the surface-activated long glass fibers 2A is strong, and since they are made of ceramic, their coefficients of thermal expansion are similar, so that the catalyst component does not fall off. In other words, even if the catalyst component 7 is not directly bonded to the wire mesh (SUS304) 1, it is firmly attached to the wire mesh (SUS304) 1 through the long glass fibers 2A, and the difference in thermal expansion between the wire mesh 1 and the catalyst component 7 is the same as that between the glass fiber and the wire mesh. It is absorbed by. Note that in FIGS. 2, 3, and 4, arrows indicate the direction of exhaust gas flow. By the way, in order to increase the abrasion strength of the catalyst layer, the sixth
As shown in the figure, a catalyst may be obtained by coating a metal plate 9 with a slurry containing a catalyst component 10 and short glass fibers 11, and drying and firing the slurry. In this case, short glass fibers 11 are used because long fibers are difficult to mix with the catalyst component and cannot be coated. As is clear from FIG. 6, when short glass fibers 11 are used, entanglement bonding between the fibers 11 cannot be expected, and the bonding between these fibers depends solely on the catalyst component 10. do. It is difficult to maintain pores between the short glass fibers 11, and therefore the activity of the catalyst layer is limited between the short glass fibers 11.
It is clear that the value is lower than that without adding 1. Furthermore, since the catalyst component is directly bonded to the plate 9, the adhesion strength is not improved at all, but rather is reduced. On the other hand, there is a method in which a catalyst component is supported on a glass cloth made of glass fibers woven into a cloth shape or a nonwoven fabric made of long glass fibers hardened with a binder, but both lack self-supporting properties and are difficult to process into a honeycomb shape. To give these catalysts independence, there are two methods: fixing them on steel plates or wire mesh with pins, or sandwiching them between wire meshes in a sandwich pattern, but these methods are expensive when producing large-area catalysts. Therefore, it is actually unsuitable. Furthermore, in particular, when long glass fibers are hardened with a binder to form a nonwoven fabric, there is a problem with the heat resistance of the binder, which limits the temperature at which it can be used. As is clear from the above explanation, the denitrification catalyst device according to the present invention uses a catalyst carrier in which long glass fibers are woven into a wire mesh, and the catalyst component is supported on this, so there is sufficient space between the long glass fibers. It holds the hole. Therefore, a catalyst can be obtained that has a high effectiveness coefficient, can efficiently proceed with the gas exchange reaction, and has little pressure loss. In addition, the catalyst component is not bonded to a wire mesh with a significantly different thermal expansion coefficient, but is bonded to long glass fibers with a similar coefficient, so whether it is used at low or high temperatures, the catalyst component (active layer ) It is possible to easily obtain a catalyst that does not cause peeling. Furthermore, since most of the catalyst component is supported inside the long glass fiber bundle, it is protected from abrasion by the long glass fibers on the surface of the bundle, resulting in a catalyst with excellent abrasion resistance. Furthermore, this catalyst is formed into a honeycomb shape and placed in the reaction tube so that the flow direction of the flue gas and the catalyst surface are parallel to each other, resulting in extremely low pressure loss and high activation effect. A denitrification catalyst device that is resistant to dust can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a partial front view of the embodiment of the present invention, Fig. 2 is a partial sectional view of the same, Fig. 3 is an enlarged sectional view of the same main part, and Fig. 4 is a partial front view of the embodiment of the present invention.
The figure is a partial perspective view of the catalyst device, FIG. 5 is a graph of experimental results, and FIG. 6 is an explanatory diagram. DESCRIPTION OF SYMBOLS 1... Wire mesh, 2... Long glass fiber bundle, 3... Catalyst carrier, 4A, 4B... Plate-shaped and mountain-shaped catalysts, 5... Reaction tube, 7... Catalyst component, 8... Holes.

Claims (1)

[Scope of utility model registration request] A catalyst in which a catalyst component is supported on a catalyst carrier made of long glass fibers woven into a wire mesh is formed into a plate shape and a mountain shape. A denitrification catalyst device, characterized in that it is arranged in a reaction tube so that the flow direction and the catalyst surface are parallel to each other.