JPS624176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a denitrification catalyst molded article with reinforced abrasion resistance at the edges, particularly at least one molded article that effectively prevents abrasion caused by soot and dust contained in the gas to be treated (gas to be denitrified).
The present invention relates to a denitrification catalyst molded product having a cylindrical shape and having a reinforced end and wear resistance.

Catalysts used for removing nitrogen oxides (NOx) contained in combustion gas and various waste gases, that is, denitration, are usually used in various shapes such as pellets, cylinders, square tubes, and plates. can do. Generally, it is often used in shapes other than pellets from the standpoint of equipment and economy.
In particular, a large number of catalyst molded products formed into a cylindrical body with one through hole or various rectangular cylindrical bodies may be stored in a denitrification device in a bundled state (see A and B in Figure 3), or in a large number. A catalyst molded product [see A and B in Figure 4] formed into a shape having several through holes (this shape is usually called a "honeycomb shape"), or a catalyst molded product having a large number of through holes. A bundle of two or more catalyst molded articles is often stored in a denitrification device and used.

On the other hand, the gas to be denitrified, for example, the combustion gas discharged from boilers, incinerators, etc., contains a large amount of soot and dust. The amount of soot and dust is relatively small, about 5 to 10 mg/Nm ³ when using heavy oil as fuel, but about 10 to 20 g/Nm ³ when using coal as fuel.
There are a lot of things. Moreover, the size of these soot dust particles is usually 100 μm or less. Therefore, the catalyst during the denitrification process is exposed to high temperatures of 300 to 400°C and contains such a large amount of soot and dust.
It will be exposed to the gas to be denitrified at a high speed of m/sec.

Moreover, the denitrification catalyst is a sintered product of metal oxides (for example, oxides of titanium, tungsten, vanadium, etc.), but its strength is low because the temperature during sintering is low in relation to the catalyst properties. low. Therefore, the denitrification catalyst is easily worn out by a large amount of dust contained in the gas to be denitrified, especially the exhaust gas of a boiler whose main fuel is coal, etc., so that it cannot be used as a catalyst as it is. One commonly thought of countermeasure is to fit a metal frame to the end of the catalyst molded product housed in the denitration equipment on the side where the gas to be denitrified is introduced; It is expensive and time-consuming to manufacture, fit, etc., and is not practical.

The inventors of the present invention have conducted various studies on how to effectively prevent abrasion caused by soot and dust on a cylindrical denitrification catalyst molded product having at least one through hole. The company succeeded in developing a catalyst molded product for denitrification.

In the present invention, "a cylindrical catalyst molded product having at least one through hole" refers to various cylindrical catalyst molded products such as a cylindrical shape or a polygonal cylindrical shape having one through hole. Any cylindrical shaped catalyst molded product having two or more through holes, for example, a cylindrical shape having many through holes with a honeycomb cross section (hereinafter referred to simply as "honeycomb cylindrical shape") It may be a catalyst molded article.

The end-reinforced wear-resistant catalyst molded article for denitrification of the present invention has two parts integrally fused to the end of a cylindrical catalyst molded article having at least one through hole. Melting point of metal oxides as main components
It is made by forming a glassy film at a temperature of 400 to 800°C.

This type of denitrification catalyst molded article usually has a length of about 300 to 1000 mm, for example 500 mm. For example, in the case of a catalyst molded product with one through hole, a large number of catalyst molded products are stored in a denitrification device in a bundle as described above, and a catalyst molded product with a relatively large number of through holes is used. In the case of a catalyst molded product having an extremely large number of through holes, such as a honeycomb cylindrical catalyst molded product, one or more of the catalyst molded products are stored in a denitrification device. Multiple units are stored in a denitrification device and used. According to the present invention, a glassy coating is formed on such a catalyst molded product on the gas introduction side end surface of the catalyst molded product, which the gas to be denitrified introduced into the denitrification device collides with at right angles, and on the end surface thereof. 50 mm or less, preferably about 10 mm or less. Since the catalyst portion covered with the glassy film loses its catalytic function, from the viewpoint of catalytic action, it is desirable that the surface area of the catalyst on which the glassy film is formed is as small as possible. However, the side wall surface (including the inner surface of the through hole) of the catalyst molded product that is parallel to the gas flow, and the portion close to the tip surface on the gas introduction side, is still at risk of being worn out due to the turbulent flow of the introduced gas. Therefore, it is desirable to form a glassy coating also on the side wall surface within the above-mentioned range.

The glassy coating applied in the present invention has a melting point of 400 to 800°C, preferably 450 to 600°C. If the melting point is less than 400℃, there is a risk that the glassy coating will melt at the temperature used as a catalyst, that is, at the denitrification reaction temperature, and it may not be able to effectively prevent wear caused by soot and dust.If the melting point exceeds 800℃, the glassy coating All of these methods are unsuitable because the heating during fusion of the coating reduces catalyst performance.

A preferable vitreous material suitable for the vitreous coating of the present invention is one whose main component is an oxide of two or more metals selected from the group of B, Si, Pb, Li, K, and Na. That is, the preferred glassy material is one whose main component is two or more oxides selected from the group consisting of boron oxide, lead oxide, silicic anhydride, lithium oxide, potassium oxide, and sodium oxide.

Particularly preferred glass materials for the glass coating of the present invention include, for example, PbO2 mol and
A glassy powder obtained by melting a mixture of 1 mole of SiO ₂ and solidifying it by cooling, and a glassy powder obtained by melting a mixture of 1 mole of PbO and 2 moles of B ₂ O ₃ and solidifying it by cooling. mixture (hereinafter referred to as “2PbO・SiO ₂
―PbO・2B ₂ O ₃ ''. ) is produced by heating and melting. This glassy material has a melting point of about 525°C.

In addition, the preferable glassy material is 2PbO・
There are B ₂ O ₃ and 3PbO・2SiO ₂ ―Na ₂ O・SiO ₂ , etc.
The melting point of the former is 493°C, and the melting point of the latter is 590°C.
Since the melting point of this type of glassy material can be changed by changing the ratio of each oxide, a glassy material with a desired melting point can be easily obtained.

It is desirable to select the composition of the vitreous material used to form the vitreous coating of the present invention, taking into consideration not only the melting point but also the coefficient of thermal expansion. If the coefficients of thermal expansion of the catalyst and the glassy material are different, the glassy coating may peel or crack during cooling after being fused to the catalyst or during use of the catalyst, making it impossible to exhibit a sufficient wear-preventing effect.

In the present invention, in order to form a glassy film on the end of a catalyst molded product, metal oxides (including composite oxides, etc.) and/or metals are heated at a rate that forms a predetermined glass composition after melting. A mixture of two or more metal salts that generate oxides in powder form is dispersed in, for example, an aqueous dispersion medium, and the dispersion is applied to a predetermined portion of the end of the catalyst molded product on which a glassy coating is to be formed. After drying, the coating film is heated and melted at a predetermined temperature to form a glassy coating and simultaneously fused.

The above dispersion for coating may optionally contain suitable deflocculants and viscosity modifiers for stably dispersing the particles, such as Kibushi clay, clay minerals such as clay, gum arabic, methyl cellulose, and polyvinyl alcohol. Can be added in small amounts.
In general, if the concentration of the dispersion is too high, it will be difficult to apply, and if it is too low, the required thickness will not be obtained in one application and multiple applications will be required, so choose an appropriate concentration. is desirable. The above 2PbO・
In the case of SiO ₂ - PbO・2B ₂ O ₃ , the solid content concentration is 70
Within the range of ~20% by weight, the desired coating thickness can be easily obtained in one coat for both brush coating and dip coating.

Formation and fusion of a glassy film by heating and melting the coating film formed as described above can be achieved by holding the film at a temperature approximately 30 to 100°C higher than its melting point for approximately 10 to 60 minutes. desirable. If the heating time is too long, a chemical reaction will occur between the catalyst component and the glassy material, generating bubbles, and if the heating time is too long, the viscosity will decrease, and the generated gas will float to the surface due to buoyancy. Both are undesirable because they generate a large number of small bubbles.

Formation of a glassy film by heating and melting and cooling after fusing are preferably carried out gradually, for example, at least one hour is required for cooling to room temperature, since cracks will occur in the glassy film if the cooling is too rapid. The thickness of the glassy film thus formed is usually 0.01 to 0.5 mm, preferably 0.05 to 0.4 mm.
It is.

In the present invention, any catalyst may be used as long as it is a denitrification catalyst as the catalyst constituting the main body of the catalyst molded article to which the glassy coating is applied. Examples include various denitration catalysts such as Ti--V type, Ti--W type oxide shaped catalysts, and shaped catalysts in which vanadium or tungsten is supported on Ti oxide shaped bodies.

Next, the present invention will be explained with reference to the accompanying drawings. 1st
The figure is a perspective view of the catalyst molded product of the present invention in which a vitreous coating is applied to the end of a cylindrical catalyst molded product, and FIG. 2 is a cylindrical catalyst molded product shown in FIG. FIG. 2 is a cross-sectional view showing the end portion of the product on which the glassy coating is formed. In each drawing,
1 is a catalyst molded product, 2 is a glassy coating formed on the end face of the catalyst molded product, 2′ is a glassy coating formed on the outer wall near the end face of the catalyst molded product, and 2″ is a glassy coating formed on the end face of the catalyst molded product. The vitreous coating formed on the inner wall of the adjacent hole, and 3 indicate the hole of the catalyst molded article, respectively.

In the case shown in FIGS. 1 and 2, a vitreous coating 2 is attached to the end of a catalyst molded product 1 formed into a cylindrical body.
2' and 2'', but this type of shaped catalyst can be formed into various rectangular cylinders, such as square cylinders and hexagonal cylinders, as mentioned above, in addition to cylindrical bodies. In addition, catalyst molded products formed into various shapes may be molded into a honeycomb cylindrical molded product having a large number of through holes. A glassy coating is applied to the end face and the outer and/or inner wall near the end face.

FIG. 3 is an end view illustrating the focusing state of the cylindrical denitrification catalyst molded product during use. That is, A in FIG. 3 is an end view showing an example of the condensation state during use of a catalyst molded product formed into a cylindrical body as shown in FIGS. 1 and 2, and B is a similar end view. Another example of the focusing state of the cylindrical catalyst molded product during use is shown in an end view, in which reference numeral 4 indicates a focusing band and reference numeral 5 indicates a focusing fixing plate. Further, FIG. 4 is a partial sectional view illustrating a honeycomb cylindrical catalyst molded product having a large number of through holes. That is, A in FIG. 4 shows a honeycomb cylindrical catalyst molded product having a through hole with a hexagonal cross section.
B in the figure shows a honeycomb cylindrical catalyst molded product having a through hole with a square cross section. In order to apply the present invention to catalyst molded articles of various shapes, a glassy coating is formed on the end of each catalyst molded article on the gas introduction side, as described above. In addition, the symbols 1 to 3 in FIGS. 3 and 4
1 and 2 indicate similar or equivalent parts to those in FIGS. 1 and 2.

Next, a description will be given with reference to comparative examples and examples.

Comparative example: Made of titanium oxide as the main component, it has 121 through holes with a square cross section of 7 mm x 7 mm, and the wall thickness of each hole is 2 mm.
mm, and the overall size is 101mm long x 101mm wide x
A sealed sand plaster that can change air pressure and dust amount was used on the end face of a honeycomb cylindrical denitrification catalyst molded product with a length of 500 mm, at a flow rate of 10 m/s and a dust amount of 500 g/Nm ³ . and temperature 20℃
When fly ash (coal dust) was sprayed under these conditions, the end face of the catalyst molded product started to wear out after about 1 minute, the end face of the catalyst molded product wore out about 1 mm in about 1 minute and 30 seconds, and after 2 minutes it started to wear out. Approximately 1.5 to 2 mm of wear occurred.

Example 1 Approximately 20% of the end portion of the honeycomb cylindrical denitrification catalyst molded product having the same square cross-sectional through holes as in the comparative example
2PbO SiO ₂ prepared as follows:
- Immerse for 30 seconds in an aqueous suspension of mixed oxide fine powder of PbO・2B ₂ O ₃ (solid content concentration 42% by weight) to form a film of the suspension on the end face and inner and outer walls of the end. formed.

Next, after drying the coating with an infrared heater, the catalyst molded product was placed in an electric furnace at 600°C.
The coating was baked for 20 minutes to melt and form a glassy coating.

When fly ash was sprayed on the end surface of the catalyst molded article having the glassy coating under the same conditions as in the comparative example, no wear was observed on the glassy coating at the end even after about 10 hours of spraying.

Preparation of oxide suspension A mixture of 2 mol of PbO and 1 mol of SiO ₂ was heated to 1050℃.
After heating and melting, it is cooled to form a glass-like substance,
This was ground into a fine powder with a particle size of 50 to 200 mesh. Further, a mixture of 1 mole of PbO and 2 moles of B ₂ O ₃ was heated and melted at 1000° C., cooled to form a glassy substance, and this was crushed to form a fine powder with a particle size of 50 to 200 mesh.

Next, these two powders were mixed at a weight ratio of 1:1, added to water, and stirred to a solid concentration of 42.
It was made into a suspension of % by weight.

Example 2 Approximately 20 mm of the end of the same honeycomb cylindrical catalyst molded product as in the comparative example was treated with 3PbO・2SiO ₂ ―Na ₂ O・
Aqueous suspension of mixed oxide fine powder of _SiO2 (solids content
40% by weight) for 30 seconds to form a film of the suspension on the end face and inner and outer walls of the end portion.

Next, after drying the coating of the catalyst molded article with an infrared heater, it was placed in an electric furnace and heated at 650°C for 20 minutes.
The film was fired for 1 minute to melt the film and form and fuse the vitreous film.

When fly ash was sprayed on the end surface of the catalyst molded article having the glassy coating under the same conditions as in the comparative example, no wear was observed on the glassy coating at the end even after about 12 hours of spraying.

[Brief explanation of the drawing]

1 and 2 illustrate a cylindrical catalyst molded article of the present invention, FIG. 1 is a partially cutaway perspective view thereof, and FIG. 2 is a vitreous coating of the molded article shown in FIG. 1. FIG. Further, A and B in FIG. 3 are end views respectively illustrating the focusing state of the cylindrical catalyst molded product shown in FIG. 1 when in use. Also, A and B in Figure 4
1 is a partial sectional view of a honeycomb cylindrical catalyst molded product having a large number of through holes with a regular hexagonal cross section and a square cross section, respectively. The symbols in each drawing indicate the following. DESCRIPTION OF SYMBOLS 1... Catalyst molded product, 2, 2', 2''... Glassy coating, 3... Through hole of catalyst molded product, 4... Band for focusing the catalyst molded product, 5... Fixing plate for focusing the catalyst molded product.

Claims (1)

[Claims] 1. A cylindrical catalyst molded product having at least one through hole, the main component being two or more metal oxides integrally fused to the end of the catalyst molded product. melting point
A denitrification catalyst molded product with reinforced edges and wear resistance formed by forming a glassy film at a temperature of 400 to 800°C. 2. The catalyst according to claim 1, wherein the glassy coating is mainly composed of oxides of two or more metals selected from the group of B, Si, Pb, Li, K, and Na. Molding. 3. A patent claim in which the glassy coating is formed by applying a mixture of two or more types of metal oxide and/or a metal salt that produces a metal oxide upon heating to the end of a catalyst molded product, and then heating and melting the mixture. The catalyst molded article according to item 1 or 2.